The word red comes from the Old English rēad. Further back, the word can be traced to the Proto-Germanic rauthaz and the Proto-Indo European root reudh-. This is the only color word which has been traced to an Indo-European root. In the English language, the word red is associated with the color of blood, certain flowers (i.e. roses), and ripe fruits (i.e. apples, cherries). Fire is also strongly connected, as is the sun and the sky at sunset. Healthy people are often said to have a redness touch to their skin color (as opposed to be appearing pale). After the rise of socialism in the mid-19th century, red was to describe revolutionary movements. The word is also obviously associated with anything of the color occupying the lower end of the visible light spectrum, such as red hair or red soil. Red Indians is a British term for Native Americans, American terms for this ethnic group include redskin, redhead and red man, though they are not the preferred terms.
Red is any of a number of similar colors evoked by light consisting predominantly of the longest wavelengths of light discernible by the human eye, in the wavelength range of roughly 630–700 nm. Longer wavelengths than this are called infrared, or below red and cannot be seen by human eyes. Red's wavelength has been an important factor in laser technologies as 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 blue lasers. Red light is also used to preserve night vision in low-light or night-time situations, as the rod cells in the human eye aren't sensitive to red. Red is used as one of the additive primary colors of light, complementary to cyan, in RGB color systems. Red is also one of the subtractive primary colors of RYB color space but not CMYK color space.
One common use of red as an additive primary color is in the RGB color model. Because "red" is not by itself standardized, color mixtures based on red are not exact specifications of color either. In order to produce exact colors the color red needs to be defined in terms of an absolute color space such as sRGB. As used in computer monitors and television screens, red is very variable, but some systems may apply color correction (so that a standardized "red" is produced that is not in fact full intensity of only the red colorant).
A red filter used in black and white photography increases contrast in most scenes. For example, combined with a polarizer, it can turn the sky black. Films simulating the effects of infrared film (such as Ilford's SFX 200) do so by being much more sensitive to red than to other colors. 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. Though many more modern darkrooms use an amber safelight, red illumination is closely associated with the darkroom in the public mind.
In astronomy, stars of spectral type M (the stars with the coolest temperature) are classified as red stars. Mars is called the Red Planet because of the reddish color imparted to its surface by the abundant iron oxide present there. Astronomical objects which are moving away from the observer exhibit a red shift. Jupiter's surface displays a Great Red Spot, a football-shaped area south of the planet's equator. Astronomers believe the spot to be some kind of storm.
Oxygenated blood is red due to the presence of oxygenated hemoglobin. Red light is the first to be absorbed by sea water, so that many fish and marine invertebrates that appear bright red are black in their native habitat. When used about 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, Robin Redbreast, Red Grouse, Red Knot, Redstart, Redwing, Red Setter, Red Devon cattle etc. The usage for animal color appears similar to that for red ochre, red hair and Red Indian. Interestingly red appears to be rarely used in names of animals which are a brighter blood-red or scarlet color (Carmine Bee-eater, Scarlet Tanager). When used for flowers, red often refers to purplish (red deadnettle, red clover, red helleborine) or pink (red campion, red valerian) colors.
Red is frequently used as a symbol of guilt, sin and anger, often as connected with blood or sex. A biblical example is found in Isaiah: "Though your sins be as scarlet, they shall be white as snow. Also, The Scarlet Letter an 1850 American novel by Nathaniel Hawthorne, features a woman in a Puritan New England community who is punished for adultery with ostracism, her sin represented by a red letter 'A' sewn into her clothes. This all comes from a general Hebrew view inherited by Christianity which associates red with the blood of murder, as well as with guilt in general. Another popular example of this is in the phrase "caught red-handed", meaning either caught in an act of crime or caught with the blood of murder still on one's hands. At one point, red was associated with prostitutes, or now, with brothels (red-light districts). In Roman Catholicism, red represents wrath, one of the Seven Deadly Sins. In Christianity, Satan is usually depicted as colored red and/or wearing a red costume in both iconography and popular culture. Statistics have shown that red cars are more likely to be involved in accidents.
The color red is associated with lust, passion, love, and beauty as well. The association with love and beauty is possibly related to the use of red roses as a love symbol. Both the Greeks and the Hebrews considered red a symbol of love, as well as sacrifice. In the metaphysics of the "New Age Prophetess", Alice Bailey, in her system called the Seven Rays which classifies humans into seven different metaphysical psychological types, the "sixth ray" of "love-devotion" is represented by the color red. People who have this metaphysical psychological type are said to be "on the Red Ray". Psychics who claim to be able to observe the aura with their third eye report that a red aura is associated with a love of sports and physical exercise.
Red catches people's attention, and is often used either in a negative way to indicate danger and emergency, or in a positive way in advertising to gain more viewers, or in nature, as a ripe fruit announces its readiness with its red color. Several studies have indicated that red carries the strongest reaction of all the colors, with the level of reaction decreasing gradually with orange, yellow, and white, respectively. Because of this, scientists have repeatedly recommended red for warning signals, labels, and signs. Because of these recommendations, red has seen widespread use as a danger signal, in stop signs, to warn people of extreme heat or flammability, and even to signal warnings in sports such as soccer (see: penalty card). It may also represent fire and so may symbolize the presence of God. It is the liturgical color for Pentecost.
In Japan, red is a traditional color for a heroic figure. In the Indian Sub-continent, red is the traditional color of bridal dresses, and is frequently represented in the media as a symbolic color for married women. The color is associated with sexuality in marriage relationships through its connection to heat and fertility. It is also the color of wealth, beauty, and the goddess Lakshmi.
In Central Africa, Ndembu warriors rub themselves with red 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. Because of the connection red bears with death in many parts of Africa, the Red Cross has changed its colors to green and white in parts of the continent.
Red is one of the most common colors used on national flags throughout the world. On these flags it carries the same meanings which it does anywhere else: 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 which once belonged to the former British Empire. The British flag bears the colors red, white and blue. red is represented by three crosses: the patron saint of England Saint George, the patron saint of Scotland, Saint Andrew and the patron saint of Ireland, Saint Patrick. The United States flag bears the colors of Britain, and other countries' flags, such as those of Australia and Fiji, carry a small inset of the British flag in memory of their ties to that country. Former colonies of Spain, such as Ecuador and Venezuela, also feature red, one of the colors of the Spanish flag, on their own banners.
Red, along with blue and white is also one of the Pan-Slavic colors adopted by the Slavic solidarity movement of the late nineteenth century. Initially, these were the colors of the Russian flag, but as the Slavic movement grew, other Slavic people began adopting them, such as Slovaks, Slovenes or Serbs. In addition to this, red, white, and black are the colors of Pan-Arabism, and are used by many Arab countries.
Red is one of the four colors (along with gold, green, and black) 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 Ethiopian flag, one of the oldest independent African countries. Rwanda, notably, removed red from its flag after the Rwandan Genocide, because Pan-Africanism was so strongly associated with the event and because of red's association with blood.
Even before Europe's Revolutions of 1848, "Socialist" red was used as a color of European Revolutionaries, often in the form of the red flag. It was also used by Garibaldi's camicie rosse ("redshirts") in the Italian Risorgimento, and taken up by Leftist and generally revolutionary groups, while the white of legitimist Bourbon partisans became associated with pre-World War I conservatives. This relates to the term "Blood of the workers", representing the suffering of the proletariat. For instance the Civil War in Russia and the Civil War in Finland were fought between the "Red Army" and various "White Armies".
The Cincinnati Red Stockings are the oldest professional baseball team, dating back to 1869. The franchise soon relocated to Boston and is now the Atlanta Braves, but its name survives as the origin for both the Cincinnati Reds and Boston Red Sox. During the 1950s when red was so strongly associated with communism, the modern Cincinnati team was known as the "Redlegs" and the term was even used on baseball cards. After the red scare faded, the team was known as the Reds again.
The identification of Communism with "Socialist" red (with the red flag being the primary color of the flag of the Soviet Union) and the red star being a Communist emblem led to such Cold War phrases as "the Red Menace" and "Red China" (distinguished from Nationalist China, "Free China," or Taiwan).
China's de-facto anthem under Mao Zedong was The East is Red. Mao Zedong was sometimes referred to as a "red sun". The color was also associated with political vehicles such as the Red Guard in China and the Red Guards during the Russian Revolution of 1917 as well as with left wing paramilitary terrorist groups such as the Red Army Faction in Germany and the Japanese Red Army. Red remains associated with parties on the left of the political spectrum. However, in the United States, a red state is one whose population predominantly supports the Republican Party. Red and black are colors associated with anarchism, and, specifically, anarcho-syndicalism.