|Wavelength||approx. 625–740  nm|
|sRGBB ( r, g, b)||(255, 0, 0)|
|B: Normalized to [0–255] (byte)|
Red is the color at the end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometres.  It is a primary color in the RGB color model and the CMYK color model, and is the complementary color of cyan. Reds range from the brilliant yellow-tinged scarlet and vermillion to bluish-red crimson, and vary in shade from the pale red pink to the dark red burgundy.  The red sky at sunset results from Rayleigh scattering, while the red color of the Grand Canyon and other geological features is caused by hematite or red ochre, both forms of iron oxide. Iron oxide also gives the red color to the planet Mars. The red color of blood comes from the protein hemoglobin, while ripe strawberries, red apples and reddish autumn leaves are colored by anthocyanins. 
Red pigment made from ochre was one of the first colors used in prehistoric art. The Ancient Egyptians and Mayans colored their faces red in ceremonies; Roman generals had their bodies colored red to celebrate victories. It was also an important color in China, where it was used to color early pottery and later the gates and walls of palaces. :60–61 In the Renaissance, the brilliant red costumes for the nobility and wealthy were dyed with kermes and cochineal. The 19th century brought the introduction of the first synthetic red dyes, which replaced the traditional dyes. Red also became the color of revolution; Soviet Russia adopted a red flag following the Bolshevik Revolution in 1917, later followed by China, Vietnam, and other communist countries.
Since red is the color of blood, it has historically been associated with sacrifice, danger and courage. Modern surveys in Europe and the United States show red is also the color most commonly associated with heat, activity, passion, sexuality, anger, love and joy. In China, India and many other Asian countries it is the color of symbolizing happiness and good fortune. :39–63
Shades and variations
Pink is a pale shade of red. Cherry blossoms in the Tsutsujigaoka Park, Sendai, Miyagi, Japan.
In science and nature
The human eye sees red when it looks at light with a wavelength between approximately 625 and 740 nanometers.  It is a primary color in the RGB color model and the light just past this range is called infrared, or below red, and cannot be seen by human eyes, although it can be sensed as heat.  In the language of optics, red is the color evoked by light that stimulates neither the S or the M (short and medium wavelength) cone cells of the retina, combined with a fading stimulation of the L (long-wavelength) cone cells. 
Primates can distinguish the full range of the colors of the spectrum visible to humans, but many kinds of mammals, such as dogs and cattle, have dichromacy, which means they can see blues and yellows, but cannot distinguish red and green (both are seen as gray). Bulls, for instance, cannot see the red color of the cape of a bullfighter, but they are agitated by its movement.  (See color vision).
One theory for why primates developed sensitivity to red is that it allowed ripe fruit to be distinguished from unripe fruit and inedible vegetation.  This may have driven further adaptations by species taking advantage of this new ability, such as the emergence of red faces. 
Red illumination was (and sometimes still is) used as a safelight while working in a darkroom as it does not expose most photographic paper and some films.  Today modern darkrooms usually use an amber safelight.
In color theory and on a computer screen
On the color wheel long used by painters, and in traditional color theory, red is one of the three primary colors, along with blue and yellow. Painters in the Renaissance mixed red and blue to make violet: Cennino Cennini, in his 15th-century manual on painting, wrote, "If you want to make a lovely violet colour, take fine lac [red lake], ultramarine blue (the same amount of the one as of the other) with a binder" he noted that it could also be made by mixing blue indigo and red hematite. 
In modern color theory, also known as the RGB color model, red, green and blue are additive primary colors. Red, green and blue light combined together makes white light, and these three colors, combined in different mixtures, can produce nearly any other color. This is the principle that is used to make all of the colors on your computer screen and your television. For example, magenta on a computer screen is made by a similar formula to that used by Cennino Cennini in the Renaissance to make violet, but using additive colors and light instead of pigment: it is created by combining red and blue light at equal intensity on a black screen. Violet is made on a computer screen in a similar way, but with a greater amount of blue light and less red light. 
In a traditional color wheel from 1708, red, yellow and blue are primary colors. Red and yellow make orange, red and blue make violet.
Tiny Red, green and blue sub-pixels (enlarged on left side of image) create the colors you see on your computer screen and TV.
Color of sunset
As a ray of white sunlight travels through the atmosphere to the eye, some of the colors are scattered out of the beam by air molecules and airborne particles due to Rayleigh scattering, changing the final color of the beam that is seen. Colors with a shorter wavelength, such as blue and green, scatter more strongly, and are removed from the light that finally reaches the eye.  At sunrise and sunset, when the path of the sunlight through the atmosphere to the eye is longest, the blue and green components are removed almost completely, leaving the longer wavelength orange and red light. The remaining reddened sunlight can also be scattered by cloud droplets and other relatively large particles, which give the sky above the horizon its red glow. 
Lasers emitting in the red region of the spectrum have been available since the invention of the ruby laser in 1960. In 1962 the red helium–neon laser was invented,  and these two types of lasers were widely used in many scientific applications including holography, and in education. Red helium–neon lasers were used commercially in LaserDisc players. The use of red laser diodes became widespread with the commercial success of modern DVD players, which use a 660 nm laser diode technology. Today, red and red-orange laser diodes are widely available to the public in the form of extremely inexpensive laser pointers. Portable, high-powered versions are also available for various applications.  More recently, 671 nm diode-pumped solid state ( DPSS) lasers have been introduced to the market for all-DPSS laser display systems, particle image velocimetry, Raman spectroscopy, and holography. 
Red's wavelength has been an important factor in laser technologies; red lasers, used in early compact disc technologies, are being replaced by blue lasers, as red's longer wavelength causes the laser's recordings to take up more space on the disc than would blue-laser recordings. 
- Mars is called the Red Planet because of the reddish color imparted to its surface by the abundant iron oxide present there. 
- Astronomical objects that are moving away from the observer exhibit a Doppler red shift.
- Jupiter's surface displays a Great Red Spot caused by an oval-shaped mega storm south of the planet's equator. 
- Red giants are stars that have exhausted the supply of hydrogen in their cores and switched to thermonuclear fusion of hydrogen in a shell that surrounds its core. They have radii tens to hundreds of times larger than that of the Sun. However, their outer envelope is much lower in temperature, giving them an orange hue. Despite the lower energy density of their envelope, red giants are many times more luminous than the Sun due to their large size.
- Red supergiants like Antares, Betelgeuse, VY Canis Majoris and UY Scuti, one of the biggest stars in the Universe, are the biggest variety of red giants. They are huge in size, with radii 200 to 2600 times greater than our Sun, but relatively cool in temperature (3000–4500 K), causing their distinct red tint. Because they are shrinking rapidly in size, they are surrounded by an envelope or skin much bigger than the star itself. The envelope of Betelgeuse is 250 times bigger than the star inside.
- A red dwarf is a small and relatively cool star, which has a mass of less than half that of the Sun and a surface temperature of less than 4,000 K. Red dwarfs are by far the most common type of star in the Galaxy, but due to their low luminosity, from Earth, none are visible to the naked eye. 
Artist's impression of a red dwarf, a small, relatively cool star that appears red due to its temperature
Pigments and dyes
Despite its yellow greenish flower, the roots of the Rubia tinctorum, or madder plant, produced the most common red dye used from ancient times until the 19th century.
Alizarin was the first synthetic red dye, created by German chemists in 1868. It duplicated the colorant in the madder plant, but was cheaper and longer lasting. After its introduction, the production of natural dyes from the madder plant virtually ceased.
Red lac, red lake and crimson lake
Red lac, also called red lake, crimson lake or carmine lake, was an important red pigment in Renaissance and Baroque art. Since it was translucent, thin layers of red lac were built up or glazed over a more opaque dark color to create a particularly deep and vivid color.
Unlike vermilion or red ochre, made from minerals, red lake pigments are made by mixing organic dyes, made from insects or plants, with white chalk or alum. Red lac was made from the gum lac, the dark red resinous substance secreted by various scale insects, particularly the Laccifer lacca from India.  Carmine lake was made from the cochineal insect from Central and South America, Kermes lake came from a different scale insect, kermes vermilio, which thrived on oak trees around the Mediterranean. Other red lakes were made from the rose madder plant and from the brazilwood tree.
Red lake pigments were an important part of the palette of 16th-century Venetian painters, particularly Titian, but they were used in all periods.  Since the red lakes were made from organic dyes, they tended to be fugitive, becoming unstable and fading when exposed to sunlight.
The most common synthetic food coloring today is Allura Red AC, a red azo dye that goes by several names including: Allura Red, Food Red 17, C.I. 16035, FD&C Red 40,   It was originally manufactured from coal tar, but now is mostly made from petroleum.
In Europe, Allura Red AC is not recommended for consumption by children. It is banned in Denmark, Belgium, France and Switzerland, and was also banned in Sweden until the country joined the European Union in 1994.  The European Union approves Allura Red AC as a food colorant, but EU countries' local laws banning food colorants are preserved. 
In the United States, Allura Red AC is approved by the Food and Drug Administration (FDA) for use in cosmetics, drugs, and food. It is used in some tattoo inks and is used in many products, such as soft drinks, children's medications, and cotton candy. On June 30, 2010, the Center for Science in the Public Interest (CSPI) called for the FDA to ban Red 40. 
Because of public concerns about possible health risks associated with synthetic dyes, many companies have switched to using natural pigments such as carmine, made from crushing the tiny female cochineal insect. This insect, originating in Mexico and Central America, was used to make the brilliant scarlet dyes of the European Renaissance.
The red of autumn leaves is produced by pigments called anthocyanins. They are not present in the leaf throughout the growing season, but are actively produced towards the end of summer.  They develop in late summer in the sap of the cells of the leaf, and this development is the result of complex interactions of many influences—both inside and outside the plant. Their formation depends on the breakdown of sugars in the presence of bright light as the level of phosphate in the leaf is reduced. 
During the summer growing season, phosphate is at a high level. It has a vital role in the breakdown of the sugars manufactured by chlorophyll. But in the fall, phosphate, along with the other chemicals and nutrients, moves out of the leaf into the stem of the plant. When this happens, the sugar-breakdown process changes, leading to the production of anthocyanin pigments. The brighter the light during this period, the greater the production of anthocyanins and the more brilliant the resulting color display. When the days of autumn are bright and cool, and the nights are chilly but not freezing, the brightest colorations usually develop.
Anthocyanins temporarily color the edges of some of the very young leaves as they unfold from the buds in early spring. They also give the familiar color to such common fruits as cranberries, red apples, blueberries, cherries, raspberries, and plums.
Anthocyanins are present in about 10% of tree species in temperate regions, although in certain areas—a famous example being New England—up to 70% of tree species may produce the pigment.  In autumn forests they appear vivid in the maples, oaks, sourwood, sweetgums, dogwoods, tupelos, cherry trees and persimmons. These same pigments often combine with the carotenoids' colors to create the deeper orange, fiery reds, and bronzes typical of many hardwood species. (See Autumn leaf color).
Blood and other reds in nature
Oxygenated blood is red due to the presence of oxygenated hemoglobin that contains iron molecules, with the iron components reflecting red light.   Red meat gets its color from the iron found in the myoglobin and hemoglobin in the muscles and residual blood. 
- When used to describe natural animal coloration, "red" usually refers to a brownish, reddish-brown or ginger color. In this sense it is used to describe coat colors of reddish-brown cattle and dogs, and in the names of various animal species or breeds such as red fox, red squirrel, red deer, European robin, red grouse, red knot, redstart, redwing, red setter, Red Devon cattle, etc. This reddish-brown color is also meant when using the terms red ochre and red hair.
- The red herring dragged across a trail to destroy the scent gets its color from the heavy salting and slow smoking of the fish, which results in a warm, brown color.
- When used for flowers, red often refers to purplish (red deadnettle, red clover, red helleborine) or pink (red campion, red valerian) colors.
Red blood cell agar. Blood appears red due to the iron molecules in blood cells.
A red setter or Irish setter
A pair of European red foxes.
The European robin or robin redbreast
A cooked lobster
Red hair occurs naturally on approximately 1–2% of the human population.  It occurs more frequently (2–6%) in people of northern or western European ancestry, and less frequently in other populations. Red hair appears in people with two copies of a recessive gene on chromosome 16 which causes a mutation in the MC1R protein. 
Red hair varies from a deep burgundy through burnt orange to bright copper. It is characterized by high levels of the reddish pigment pheomelanin (which also accounts for the red color of the lips) and relatively low levels of the dark pigment eumelanin. The term redhead (originally redd hede) has been in use since at least 1510.  Cultural reactions have varied from ridicule to admiration; many common stereotypes exist regarding redheads and they are often portrayed as fiery-tempered.
In animal and human behavior
Red is associated with dominance in a number of animal species.  For example, in mandrills, red coloration of the face is greatest in alpha males, increasingly less prominent in lower ranking subordinates, and directly correlated with levels of testosterone.  Red can also affect the perception of dominance by others, leading to significant differences in mortality, reproductive success and parental investment between individuals displaying red and those not.  In humans, wearing red has been linked with increased performance in competitions, including professional sport   and multiplayer video games.  Controlled tests have demonstrated that wearing red does not increase performance or levels of testosterone during exercise, so the effect is likely to be produced by perceived rather than actual performance.  Judges of tae kwon do have been shown to favor competitors wearing red protective gear over blue,  and, when asked, a significant majority of people say that red abstract shapes are more "dominant", "aggressive", and "likely to win a physical competition" than blue shapes.  In contrast to its positive effect in physical competition and dominance behavior, exposure to red decreases performance in cognitive tasks  and elicits aversion in psychological tests where subjects are placed in an "achievement" context (e.g. taking an IQ test). 
History and art
Inside cave 13B at Pinnacle Point, an archeological site found on the coast of South Africa, paleoanthropologists in 2000 found evidence that, between 170,000 and 40,000 years ago, Late Stone Age people were scraping and grinding ochre, a clay colored red by iron oxide, probably with the intention of using it to color their bodies. 
Red hematite powder was also found scattered around the remains at a grave site in a Zhoukoudian cave complex near Beijing. The site has evidence of habitation as early as 700,000 years ago. The hematite might have been used to symbolize blood in an offering to the dead. :4
In ancient Egypt, red was associated with life, health, and victory. Egyptians would color themselves with red ochre during celebrations.  Egyptian women used red ochre as a cosmetic to redden cheeks and lips  and also used henna to color their hair and paint their nails. 
In Renaissance painting, red was used to draw the attention of the viewer; it was often used as the color of the cloak or costume of Christ, the Virgin Mary, or another central figure. In Venice, Titian was the master of fine reds, particularly vermilion; he used many layers of pigment mixed with a semi-transparent glaze, which let the light pass through, to create a more luminous color.
Woman with a wine glass, by Johannes Vermeer (1659–60). Vermeer used different shades and tints of vermilion to paint the red skirt, then glazed it with madder lake to make a more luminous color.
During the French Revolution, the Jacobins and other more radical parties adopted the red flag; it was taken from red flags hoisted by the French government to declare a state of siege or emergency. Many of them wore a red Phrygian cap, or liberty cap, modeled after the caps worn by freed slaves in Ancient Rome. During the height of the Reign of Terror, Women wearing red caps gathered around the guillotine to celebrate each execution. They were called the "Furies of the guillotine". The guillotines used during the Reign of Terror in 1792 and 1793 were painted red, or made of red wood. During the Reign of Terror a statue of a woman titled liberty, painted red, was placed in the square in front of the guillotine. After the end of the Reign of Terror, France went back to the blue, white and red tricolor, whose red was taken from the red and blue colors of the city of Paris, and was the traditional color of Saint Denis, the Christian martyr and patron saint of Paris.
In the 20th century, red was the color of Revolution; it was the color of the Bolshevik Revolution in 1917 and of the Chinese Revolution of 1949, and later of the Cultural Revolution. Red was the color of communist parties from Eastern Europe to Cuba to Vietnam.
In the late 19th and early 20th century, the German chemical industry invented two new synthetic red pigments: cadmium red, which was the color of natural vermilion, and mars red, which was a synthetic red ochre, the color of the very first natural red pigment.
Courage and sacrifice
Surveys show that red is the color most associated with courage. :43 In western countries red is a symbol of martyrs and sacrifice, particularly because of its association with blood.  Beginning in the Middle Ages, the Pope and Cardinals of the Roman Catholic Church wore red to symbolize the blood of Christ and the Christian martyrs. The banner of the Christian soldiers in the First Crusade was a red cross on a white field, the St. George's Cross. According to Christian tradition, Saint George was a Roman soldier who was a member of the guards of the Emperor Diocletian, who refused to renounce his Christian faith and was martyred. The Saint George's Cross became the Flag of England in the 16th century, and now is part of the Union Flag of the United Kingdom, as well as the Flag of the Republic of Georgia. :36
The Crucified Martyr (Saint Julia) by the Dutch artist Hieronymus Bosch. Saint Julia wears red, the traditional color of Christian martyrs.
Roman Catholic Popes wear red as the symbol of the blood of Christ. This is Pope Innocent III, in about 1219.
Hatred, anger, aggression, passion, heat and war
While red is the color most associated with love, it also the color most frequently associated with hatred, anger, aggression and war. People who are angry are said to " see red." Red is the color most commonly associated with passion and heat. In ancient Rome, red was the color of Mars, the god of war—the planet Mars was named for him because of its red color. :42, 53
Warning and danger
Red is the traditional color of warning and danger, and is therefore often used on flags. In the Middle Ages, a red flag shown in warfare indicated the intent to fight "mortal warfare," where the opposition would be slaughtered with none spared or taken prisoner taken for ransom.   Similarly, a red flag hoisted by a pirate ship meant no mercy would be shown to their target.   In Britain, in the early days of motoring, motor cars had to follow a man with a red flag who would warn horse-drawn vehicles, before the Locomotives on Highways Act 1896 abolished this law.  In automobile races, the red flag is raised if there is danger to the drivers.  In international football, a player who has made a serious violation of the rules is shown a red penalty card and ejected from the game. 
Several studies have indicated that red carries the strongest reaction of all the colors, with the level of reaction decreasing gradually with the colors orange, yellow, and white, respectively.   For this reason, red is generally used as the highest level of warning, such as threat level of terrorist attack in the United States. In fact, teachers at a primary school in the UK have been told not to mark children's work in red ink because it encourages a "negative approach". 
Red is the international color of stop signs and stop lights on highways and intersections. It was standardized as the international color at the Vienna Convention on Road Signs and Signals of 1968. It was chosen partly because red is the brightest color in daytime (next to orange), though it is less visible at twilight, when green is the most visible color. Red also stands out more clearly against a cool natural backdrop of blue sky, green trees or gray buildings. But it was mostly chosen as the color for stoplights and stop signs because of its universal association with danger and warning. :54 The 1968 Vienna Convention on Road Signs and Signals of 1968 uses red color also for the margin of danger warning sign, give way signs and prohibitory signs, following the previous German-type signage (established by Verordnung über Warnungstafeln für den Kraftfahrzeugverkehr in 1927).
The standard international stop sign, following the Vienna Convention on Road Signs and Signals of 1968
Footballer Nemanja Vidić is shown a red card and ejected from a soccer match
Red is the color of a severe terrorist threat level in the United States, under the Homeland Security Advisory System.
The color that attracts attention
Red is the color that most attracts attention. Surveys show it is the color most frequently associated with visibility, proximity, and extroverts.[ citation needed] It is also the color most associated with dynamism and activity. :48, 58
Red is used in modern fashion much as it was used in Medieval painting; to attract the eyes of the viewer to the person who is supposed to be the center of attention. People wearing red seem to be closer than those dressed in other colors, even if they are actually the same distance away. :48, 58 Monarchs, wives of presidential candidates and other celebrities often wear red to be visible from a distance in a crowd. It is also commonly worn by lifeguards and others whose job requires them to be easily found.[ citation needed]
Because red attracts attention, it is frequently used in advertising, though studies show that people are less likely to read something printed in red because they know it is advertising, and because it is more difficult visually to read than black and white text. :60
Seduction, sexuality and sin
Red by a large margin is the color most commonly associated with seduction, sexuality, eroticism and immorality, possibly because of its close connection with passion and with danger. :55
Red was long seen as having a dark side, particularly in Christian theology. It was associated with sexual passion, anger, sin, and the devil.   In the Old Testament of the Bible, the Book of Isaiah said: "Though your sins be as scarlet, they shall be white as snow."  In the New Testament, in the Book of Revelation, the Antichrist appears as a red monster, ridden by a woman dressed in scarlet, known as the Whore of Babylon. 
Satan is often depicted as colored red and/or wearing a red costume in both iconography and popular culture.   By the 20th century, the devil in red had become a folk character in legends and stories. The devil in red appears more often in cartoons and movies than in religious art.
In 17th-century New England, red was associated with adultery. In the 1850 novel by Nathaniel Hawthorne, The Scarlet Letter, set in a Puritan New England community, a woman is punished for adultery with ostracism, her sin represented by a red letter 'A' sewn onto her clothes.  
Red is still commonly associated with prostitution. At various points in history, prostitutes were required to wear red to announce their profession.  Houses of prostitution displayed a red light. Beginning in the early 20th century, houses of prostitution were allowed only in certain specified neighborhoods, which became known as red-light districts. Large red-light districts are found today in Bangkok and Amsterdam.
In both Christian and Hebrew tradition, red is also sometimes associated with murder or guilt, with "having blood on one's hands", or "being caught red-handed. 
The Whore of Babylon, depicted in a 14th-century French illuminated manuscript. The woman appears attractive, but is wearing red under her blue garment.
Reine de joie, (Queen of Joy), a book cover illustration by Henri de Toulouse-Lautrec (1892) about a Paris prostitute
Sheet music for "At the Devil's Ball", by Irving Berlin, United States, 1915.
Red in cultures and traditions
In China, red ( simplified Chinese: 红; traditional Chinese: 紅; pinyin: hóng) is the symbol of fire and the south (both south in general and Southern China specifically). It carries a largely positive connotation, being associated with courage, loyalty, honor, success, fortune, fertility, happiness, passion, and summer.   In Japan, red is a traditional color for a heroic figure.  In the Indian subcontinent, red is the traditional color of bridal dresses, and is frequently represented in the media as a symbolic color for married women.  In Central Africa, Ndembu warriors rub themselves with red paint during celebrations. Since their culture sees the color as a symbol of life and health, sick people are also painted with it. Like most Central African cultures, the Ndembu see red as ambivalent, better than black but not as good as white.  In other parts of Africa, however, red is a color of mourning, representing death. 
Red is predominant in the Russian ritual textile Rushnyk
In Christianity, red is associated with the blood of Christ and the sacrifice of martyrs. In the Roman Catholic Church it is also associated with pentecost and the Holy Spirit. In Buddhism, red is one of the five colors which are said to have emanated from the Buddha when he attained enlightenment, or nirvana. In the Shinto religion of Japan, the gateways of temples, called torii, are traditionally painted vermilion red and black. The torii symbolizes the passage from the profane world to a sacred place. The bridges in the gardens of Japanese temples are also painted red.
The red uniform
The red military uniform was adopted by the English Parliament's New Model Army in 1645, and was still worn as a dress uniform by the British Army until the outbreak of the First World War in August 1914. Ordinary soldiers wore red coats dyed with madder, while officers wore scarlet coats dyed with the more expensive cochineal. :168–69 This led to British soldiers being known as red coats.
In the modern British army, scarlet is still worn by the Foot Guards, the Life Guards, and by some regimental bands or drummers for ceremonial purposes. Officers and NCOs of those regiments which previously wore red retain scarlet as the color of their "mess" or formal evening jackets. The Royal Gibraltar Regiment has a scarlet tunic in its winter dress.
Scarlet is worn for some full dress, military band or mess uniforms in the modern armies of a number of the countries that made up the former British Empire. These include the Australian, Jamaican, New Zealand, Fijian, Canadian, Kenyan, Ghanaian, Indian, Singaporean, Sri Lankan and Pakistani armies. 
The musicians of the United States Marine Corps Band wear red, following an 18th-century military tradition that the uniforms of band members are the reverse of the uniforms of the other soldiers in their unit. Since the US Marine uniform is blue with red facings, the band wears the reverse.
Red Serge is the uniform of the Royal Canadian Mounted Police, created in 1873 as the North-West Mounted Police, and given its present name in 1920. The uniform was adapted from the tunic of the British Army. Cadets at the Royal Military College of Canada also wear red dress uniforms.
The Brazilian Marine Corps wears a red dress uniform.
The scarlet uniform of the National Guards Unit of Bulgaria
Musicians of the United States Marine Corps Band
Officer of the Royal Canadian Mounted Police
The Brazilian Marine Corps wears a dress uniform called A Garança.
The first known team sport to feature red uniforms was chariot racing during the late Roman Empire. The earliest races were between two chariots, one driver wearing red, the other white. Later, the number of teams was increased to four, including drivers in light green and sky blue. Twenty-five races were run in a day, with a total of one hundred chariots participating. 
Today many sports teams throughout the world feature red on their uniforms. Along with blue, red is the most commonly used non-white color in sports. Numerous national sports teams wear red, often through association with their national flags. A few of these teams feature the color as part of their nickname such as Spain (with their association football (soccer) national team nicknamed La Furia Roja or "The Red Fury") and Belgium (whose football team bears the nickname Rode Duivels or "Red Devils").
In club association football (soccer), red is a commonly used color throughout the world. A number of teams' nicknames feature the color. A red penalty card is issued to a player who commits a serious infraction: the player is immediately disqualified from further play and his team must continue with one less player for the game's duration.
Rosso Corsa is the red international motor racing color of cars entered by teams from Italy. Since the 1920s Italian race cars of Alfa Romeo, Maserati, Lancia, and later Ferrari and Abarth have been painted with a color known as rosso corsa ("racing red"). National colors were mostly replaced in Formula One by commercial sponsor liveries in 1968, but unlike most other teams, Ferrari always kept the traditional red, although the shade of the color varies.
The color is commonly used for professional sports teams in Canada and the United States with eleven Major League Baseball teams, eleven National Hockey League teams, seven National Football League teams and eleven National Basketball Association teams prominently featuring some shade of the color. The color is also featured in the league logos of Major League Baseball, the National Football League and the National Basketball Association.  In the National Football League, a red flag is thrown by the head coach to challenge a referee's decision during the game. During the 1950s when red was strongly associated with communism in the United States, the modern Cincinnati Reds team was known as the "Redlegs" and the term was used on baseball cards. After the red scare faded, the team was known as the "Reds" again. 
In boxing, red is often the color used on a fighter's gloves. George Foreman wore the same red trunks he used during his loss to Muhammad Ali when he defeated Michael Moorer 20 years later to regain the title he lost. Boxers named or nicknamed "red" include Red Burman, Ernie "Red" Lopez, and his brother Danny "Little Red" Lopez.
In martial arts, a red belt shows a high degree of proficiency, second only, in some schools, to the black belt.
Red is one of the most common colors used on national flags. The use of red has similar connotations from country to country: the blood, sacrifice, and courage of those who defended their country; the sun and the hope and warmth it brings; and the sacrifice of Christ's blood (in some historically Christian nations) are a few examples. Red is the color of the flags of several countries that once belonged to the British Empire. The British flag bears the colors red, white and blue; it includes the cross of Saint George, patron saint of England, and the saltire of Saint Patrick, patron saint of Ireland, both of which are red on white. :10 The flag of the United States bears the colors of Britain,  the colors of the French tricolore include red as part of the old Paris coat of arms, and other countries' flags, such as those of Australia, New Zealand, and Fiji, carry a small inset of the British flag in memory of their ties to that country. :13–20 Many former colonies of Spain, such as Mexico, Colombia, Costa Rica, Cuba, Ecuador, Panama, Peru, Puerto Rico and Venezuela, also feature red-one of the colors of the Spanish flag-on their own banners. Red flags are also used to symbolize storms, bad water conditions, and many other dangers. Navy flags are often red and yellow. Red is prominently featured in the flag of the United States Marine Corps.
Red, blue, and white are also the Pan-Slavic colors adopted by the Slavic solidarity movement of the late nineteenth century. Initially these were the colors of the Russian flag; as the Slavic movement grew, they were adopted by other Slavic peoples including Slovaks, Slovenes, and Serbs. The flags of the Czech Republic and Poland use red for historic heraldic reasons (see Coat of arms of Poland and Coat of arms of the Czech Republic) & not due to Pan-Slavic connotations. In 2004 Georgia adopted a new white flag, which consists of four small and one big red cross in the middle touching all four sides.
Red, white, and black were the colors of the German Empire from 1870 to 1918, and as such they came to be associated with German nationalism. In the 1920s they were adopted as the colors of the Nazi flag. In Mein Kampf, Hitler explained that they were "revered colors expressive of our homage to the glorious past." The red part of the flag was also chosen to attract attention – Hitler wrote: "the new flag ... should prove effective as a large poster" because "in hundreds of thousands of cases a really striking emblem may be the first cause of awakening interest in a movement." The red also symbolized the social program of the Nazis, aimed at German workers.  Several designs by a number of different authors were considered, but the one adopted in the end was Hitler's personal design. 
Red, gold, green, and black are the colors of Pan-Africanism. Several African countries thus use the color on their flags, including South Africa, Ghana, Senegal, Mali, Ethiopia, Togo, Guinea, Benin, and Zimbabwe. The Pan-African colors are borrowed from the flag of Ethiopia, one of the oldest independent African countries.   Rwanda, notably, removed red from its flag after the Rwandan genocide because of red's association with blood. 
The flags of Japan and Bangladesh both have a red circle in the middle of different colored backgrounds. The flag of the Philippines has a red trapezoid on the bottom signifying blood, courage, and valor (also, if the flag is inverted so that the red trapezoid is on top and the blue at the bottom, it indicates a state of war). The flag of Singapore has a red rectangle on the top. The field of the flag of Portugal is green and red. The Ottoman Empire adopted several different red flags during the six centuries of its rule, with the successor Republic of Turkey continuing the 1844 Ottoman Flag.
The flag of the Byzantine Empire from 1260 to its fall in 1453
The maple leaf flag of Canada, adopted in 1965. The red color comes from the Saint George's Cross of England.
Use by political movements
In 18th-century Europe, red was usually associated with the monarchy and with those in power. The Pope wore red, as did the Swiss Guards of the Kings of France, the soldiers of the British Army and the Danish Army.
The French Revolution saw red used by the Jacobins as a symbol of the martyrs of the Revolution. In the nineteenth century, with the Industrial Revolution and the rise of worker's movements, it became the color of socialism (especially the Marxist variant), and, with the Paris Commune of 1870, of revolution.
Red also became the color of many social democratic parties in Europe, including the Labour Party in Britain (founded 1900); the Social Democratic Party of Germany (whose roots went back to 1863) and the French Socialist Party, which dated back under different names, to 1879. The Socialist Party of America (1901–72) and the Communist Party USA (1919) both also chose red as their color.
Members of the Christian-Social People's Party in Liechtenstein (founded 1918) advocated an expansion of democracy and progressive social policies, and were often referred to disparagingly as "Reds" for their social liberal leanings and party colors. 
The Communist Party of China, founded in 1920, adopted the red flag and hammer and sickle emblem of the Soviet Union, which became the national symbols when the Party took power in China in 1949. Under Party leader Mao Zedong, the Party anthem became " The East Is Red",  and Mao Zedong himself was sometimes referred to as a "red sun".  During the Cultural Revolution in China, Party ideology was enforced by the Red Guards, and the sayings of Mao Zedong were published as a small red book in hundreds of millions of copies. Today the Communist Party of China claims to be the largest political party in the world, with eighty million members. 
Beginning in the 1960s and the 1970s, paramilitary extremist groups such as the Red Army Faction in Germany, the Japanese Red Army and the Shining Path Maoist movement in Peru used red as their color. But in the 1980s, some European socialist and social democratic parties, such as the Labour Party in Britain and the Socialist Party in France, moved away from the symbolism of the far left, keeping the red color but changing their symbol to a less-threatening red rose.
Red is used around the world by political parties of the left or center-left. In the United States, it is the color of the Communist Party USA, of the Social Democrats, USA, and in Puerto Rico, of the Popular Democratic Party of Puerto Rico.
In the United States, political commentators often refer to the "red states", which traditionally vote for Republican candidates in presidential elections, and "blue states", which vote for the Democratic candidate. This convention is relatively recent: before the 2000 presidential election, media outlets assigned red and blue to both parties, sometimes alternating the allocation for each election. Fixed usage was established during the 39-day recount following the 2000 election, when the media began to discuss the contest in terms of "red states" versus "blue states". 
Social and special interest groups
Such names as Red Club (a bar), Red Carpet (a discothèque) or Red Cottbus and Club Red (event locations) suggest liveliness and excitement. The Red Hat Society is a social group founded in 1998 for women 50 and over. Use of the color red to call attention to an emergency situation is evident in the names of such organizations as the Red Cross (humanitarian aid), Red Hot Organization (AIDS support), and the Red List of Threatened Species (of IUCN). In reference to humans, term "red" is often used in the West to describe the indigenous peoples of the Americas. 
Many idiomatic expressions exploit the various connotations of red:
- Expressing emotion
- "to see red" (to be angry or aggressive)
- "to have red ears / a red face" (to be embarrassed)
- "to paint the town red" (to have an enjoyable evening, usually with a generous amount of eating, drinking, dancing)
- Giving warning
- "to raise a red flag" (to signal that something is problematic)
- "like a red rag to a bull" (to cause someone to be enraged)
- "to be in the red" (to be losing money, from the accounting convention of writing deficits and losses in red ink)
- Calling attention
- "a red letter day" (a special or important event, from the medieval custom of printing the dates of saints' days and holy days in red ink.)
- "to print in red ink" (for emphasis or easy identification)
- "to lay out the red carpet" or "give red-carpet treatment" (to treat someone royally as a very special person)
- "to catch someone red-handed" (in the act of doing something wrong, such with blood on his hands after a murder or poaching game)
- Other idioms
- "to tie up in red tape". In England red tape was used by lawyers and government officials to identify important documents. It became a term for excessive bureaucratic regulation. It was popularized in the 19th century by the writer Thomas Carlyle, who complained about "red-tapism". 
- " red herring." A false clue that leads investigators off the track. Refers to the practice of using a fragrant smoked fish to distract hunting or tracking dogs from the track they are meant to follow.
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