Red

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 625–740 nm. Longer wavelengths than this are called infrared (below red), and cannot be seen by the naked human eye. 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.

In human color psychology, red is associated with heat, energy, and blood, and emotions that "stir the blood", including anger, passion, and love.

1 Etymology and definitions

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.[6] In Sanskrit, the word rudra means red. In the English language, the word red is associated with the color of blood, certain flowers (e.g. roses), and ripe fruits (e.g. apples, cherries). Fire is also strongly connected, as is the sun and the sky at sunset. Healthy light-skinned people are sometimes said to have a "ruddy" complexion (as opposed to 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.

2 Colorimetry, color science, vision, and photography

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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 approximately 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.

2.1 Symbolism

Red is 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. Often, things will be in red to scare. 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. In Sderot, Israel rockets form gaza [controlled by palestine] hit Sderot in a uncontrolled fashion sirens form radars announce Tzeveh Adom which means color red which is warning for civilians that they have 15 seconds to get to shelter

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. Psychological research has shown that men find women who are wearing red more attractive.

2.1.1 Courage and Sacrifice

Red is used as a symbol of courage and sacrifice, as in blood spilt in sacrifice or courage in the face of lethal danger. Examples of this are found in the flags of many nations including the United States, as well as in the novel The Red Badge of Courage, in which a soldier in the American Civil War discovers the meaning of courage. Besides the association with guilt previously mentioned, in Christianity, red represents the color of Christian martyrs who suffered death for their faith. It is sometimes used for Holy Thursday and during Eastertide, and red green and white is the color scheme of Christmas. In Roman Catholic tradition it is used for all feast days of Christian martyrs as well as Palm Sunday in anticipation of the death of Jesus. Red is associated in Roman mythology with the god of war, Mars. A Roman general receiving a triumph had his entire body painted red in honor of his achievement. The phrase "red-blooded" describes someone who is audacious, robust, or virile. In English heraldry, red (called gules) denoted ardent affection or love, while crimson (blood-color) stood for boldness, enthusiasm, or impetuosity. In Edward de Bono's book Six Thinking Hats a red hat represents feelings and emotions.

2.1.2 Warning

Red catches people's attention, and can be 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, red is often used to catch people's attention in a variety of situations (see: penalty card).

The port, or left, side of a sea-going vessel carries a red navigation light, to warn other vessels approaching from that side to change course to avoid a collision.