Red is the color at the longer-wavelengths end of the spectrum of visible light next to orange, at the opposite end from violet. Red color has a predominant light wavelength of roughly 620–740 nanometers. Light with a longer wavelength than red but shorter than terahertz radiation and microwave is called infrared.
Red is one of the additive primary colors of visible light, along with green and blue, which in Red Green Blue (RGB) color systems are combined to create all the colors on a computer monitor or television screen. Red is also one of the subtractive primary colors, along with yellow and blue, of the RYB color space and traditional color wheel used by painters and artists. Reds can vary in shade from very light pink to very dark maroon or burgundy; and in hue from the bright orange-red scarlet or vermilion to the bluish-red crimson. Red is the complementary color of cyan.
In nature, the red color of blood comes from hemoglobin, the iron-containing protein found in the red blood cells of all vertebrates. The red color of the Grand Canyon and other geological features is caused by hematite or red ochre, both forms of iron oxide. It also causes the red color of the planet Mars. The red sky at sunset and sunrise is caused by an optical effect known as Rayleigh scattering, which, when the sun is low or below the horizon, increases the red-wavelength light that reaches the eye. The color of autumn leaves is caused by pigments called anthocyanins, which are produced towards the end of summer, when the green chlorophyll is no longer produced. One to two percent of the human population has red hair; the color is produced 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.
Since red is the color of blood, it has historically been associated with sacrifice, danger and courage. Modern surveys in the United States and Europe 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.
Etymology and definitions
The word red is derived from the Old English rēad. The word can be further traced to the Proto-Germanic rauthaz and the Proto-Indo European root rewdʰ-. In Sanskrit, the word rudhira means red or blood. In the Akkadian language of Ancient Mesopotamia and in the modern Inuit language of Inuit, the word for red is the same word as "like blood".
The words for 'colored' in Latin (coloratus) and Spanish (colorado) both also mean 'red.' In Portuguese the word for red is vermelho, which comes from Latin "vermiculus", meaning "little worm".
In the Russian language, the word for red, Кра́сный (krasniy), comes from the same old Slavic root as the words for "beautiful"—красивый (krasiviy) and "excellent"—прекрасный (prekrasniy). Thus Red Square in Moscow, named long before the Russian Revolution, meant simply "Beautiful Square". In heraldry, the word gules is used for red.
Red in the 20th and 21st century
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.
The French painter Henri Matisse (1869–1954) was one of the first prominent painters to use the new cadmium red. He even tried, without success, to persuade the older and more traditional Renoir, his neighbor in the south of France, to switch from vermilion to cadmium red.
Matisse was also one of the first 20th-century artists to make color the central element of the painting, chosen to evoke emotions. "A certain blue penetrates your soul", he wrote. "A certain red affects your blood pressure." He also was familiar with the way that complementary colors, such as red and green, strengthened each other when they were placed next to each other. He wrote, "My choice of colors is not based on scientific theory; it is based on observation, upon feelings, upon the real nature of each experience ... I just try to find a color which corresponds to my feelings."
Later in the century, the American artist Mark Rothko (1903–1970) also used red, in even simpler form, in blocks of dark, somber color on large canvases, to inspire deep emotions. Rothko observed that color was "only an instrument;" his interest was "in expressing human emotions tragedy, ecstasy, doom, and so on."
Rothko also began using the new synthetic pigments, but not always with happy results. In 1962 he donated to Harvard University a series of large murals of the Passion of Christ whose predominant colors were dark pink and deep crimson. He mixed mostly traditional colors to make the pink and crimson; synthetic ultramarine, cerulean blue, and titanium white, but he also used two new organic reds, Naphtol and Lithol. The Naphtol did well, but the Lithol slowly changed color when exposed to light. Within five years the deep pinks and reds had begun to turn light blue, and by 1979 the paintings were ruined and had to be taken down.