Yellow is the color evoked by light that stimulates both the L and M (long- and medium-wavelength) cone cells of the retina about equally, but does not significantly stimulate the S (short-wavelength) cone cells; that is, light with much red and green but not very much blue. Light with a wavelength of 570–580 nm is yellow, as is light with a suitable mixture of somewhat longer and shorter wavelengths. Yellow's traditional RYB complementary color is purple, violet or indigo. Yellow's colorimetrically defined complementary color in both RGB and CMYK color spaces is blue.
Process yellow (also known as pigment yellow, printer's yellow or canary yellow) is one of the three colors typically used as subtractive primary colors, along with magenta and cyan. The CMYK system for color printing is based on using four inks, one of which is a yellow color. This is not in itself a standard color, though a fairly narrow range of yellow inks or pigments are used. Process yellow is based on a colorant that reflects the preponderance of red and green light, and absorbs most blue light, as in the reflectance spectra shown in the figure on the lower right.
Because of the characteristics of paint pigments and use of different color wheels, painters traditionally regard the complement of yellow as the color indigo or blue-violet.
Process yellow is not an RGB color, and there is no fixed conversion from CMYK primaries to RGB. Different formulations are used for printer's ink, so there can be variations in the printed color that is pure yellow ink.
Etymology and definitions
The word yellow comes from the Old English geolu, or geolwe which derived from the Proto-Germanic word gelwaz. The oldest known usage of this word in English is in the Old English poem Beowulf, in a description of a shield made of wood from a yew tree. In the English language, yellow is used to describe objects having the color between green and orange in the visible light spectrum (gold, egg yolks, sunflowers, etc.). The color is associated with age and aging, both with people and objects (i.e. yellowed-paper). Ethnographically, the term yellow has also been used as a slang term for both oriental persons and light-skinned African-Americans. The term is associated at times with jealousy, as well as cowardliness. Lastly, it is associated with sensational journalistic practices, or yellow journalism, and resistance to militant trade unions.
Complements of yellow
Hunt defines that "two colors are complementary when it is possible to reproduce the tristimulus values of a specified achromatic stimulus by an additive mixture of these two stimuli." That is, when two colored lights can be mixed to match a specified white (achromatic, non-colored) light, the colors of those two lights are complementary. This definition, however, does not constrain what version of white will be specified. In the nineteenth century, the scientists Grassmann and Helmholtz did experiments in which they concluded that finding a good complement for spectral yellow was difficult, but that the result was indigo, that is, a wavelength that today's color scientists would call violet. Helmholtz says "Yellow and indigo blue" are complements. Grassman reconstructs Newton's category boundaries in terms of wavelengths and says "This indigo therefore falls within the limits of color between which, according to Helmholtz, the complementary colors of yellow lie." Newton's own color circle has yellow directly opposite the boundary between indigo and violet. These results, that the complement of yellow is a wavelength shorter than 450 nm, are derivable from the modern CIE 1931 system of colorimetry if it is assumed that the yellow is about 580 nm or shorter wavelength, and the specified white is the color of a blackbody radiator of temperature 2800 K or lower (that is, the white of an ordinary incandescent light bulb). More typically, with a daylight-colored or around 5000 to 6000 K white, the complement of yellow will be in the blue wavelength range, which is the standard modern answer for the complement of yellow.
Plants and animals
The yellow birch (Betula alleghaniensis) is a birch species native to eastern North America, from Nova Scotia, New Brunswick, and southern Quebec west to Minnesota, and south in the Appalachian Mountains to northern Georgia. They are medium-sized deciduous trees and can reaching about 20 m tall, trunks up to 80 cm in diameter. The bark is smooth and yellow-bronze and the wood is extensively used for flooring, cabinetry, and toothpicks.
Yellow-breasted Chats (Icteria virens) are large foraging songbird found in southern parts of Canada, the United States, Mexico, and Central America. They are olive with a white bellies and a yellow throat and breast, with a long tail, a thick heavy bill, a large white eye ring, and dark legs.
A yellow-fever mosquito is a mosquito in the Aedes genus, so named because they transmit dengue fever and yellow fever, the mosquito-born viruses.
Yellow-green alga, also called xanthophytes, are a class of algae in the Heterokontophyta division. Most live in freshwater, but some are found in marine and soil habitats. They vary from single-celled flagellates to simple colonial and filamentousforms. Unlike other heterokonts, yellow-green algae's chloroplasts do not contain fucoxanthin, which is why they have a lighter color.
The Yellowhammer (Emberiza citrinella) is a passerine in the bunting family Emberizidae. It breeds across Europe and much of Asia. Most yellowhammers are resident, but some far northern birds migrate south in winter. It is common in all sorts of open areas with some scrub or trees. They are large with a thick seed-eater's bill. The males have a bright yellow head, yellow underparts, and a heavily streaked brown back. Females are much duller and more streaked below.
Yellowjackets are black-and-yellow wasps of the genus Vespula or Dolichovespula (though some can be black-and-white, the most notable of these being the bald-faced hornet, Dolichovespula maculata). They can be identified by their distinctive black-and-yellow color, small size (slightly larger than a bee), and entirely black antennae.
Yellow poplar is a common name for Liriodendron, the tuliptree. The name is inaccurate as this genus is not related to poplars.
The Yellow-shafted Flicker (Colaptes auratus) is a large woodpecker species of eastern North America. They have yellow shafts on their wing and tail feathers.
Yellowtail is the common name for dozens of different fish species that have yellow tails or a yellow body.
Goldenrod is a yellow flowering plant in the Family Asteraceae
Yellow in human culture
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Stars of spectral class G, such as our sunSol, have a color temperature that we characterize as "yellowish".
The planet Saturn is yellowish, like a class G star.
Yellow is associated with Monday on the Thai solar calendar. Anyone may wear yellow on Mondays, and anyone born on a Monday may adopt yellow as their color.
In the English language, yellow has traditionally been associated with jaundice and cowardice. In American slang, a coward is said to be "yellowbellied" or "yellow".
"Yellow" ("giallo"), in Italy, refers to crime stories, both fictional and real. This association began about in 1930 because the first series of crime novels published in Italy had a yellow cover.
Pencils are often painted yellow, originally because of the association of this color with the orient, where the best graphite was found.
Asian people are sometimes referred to as the yellow race. The use of "yellow" to refer to people of East Asian descent is usually regarded as offensive today in most contexts. In the 20th-century United States, immigrants from China and other East Asian nations were derogatorily referred to as a "yellow peril."
A High yellow is African-American slang for a someone who is a very light-skinned African-American. This term was widely used in the early 20th century but it is seldom heard nowadays.
Yellow is the color of the snooker ball that has a 2-point value.
The legendary first emperor of China was known as the Yellow Emperor or Huang Di (Chinese: 黃帝, Simplified Chinese: 黄帝).
The Yellow Turbans were a Daoist sect that staged an extensive rebellion during the Han Dynasty.
"Yellow journalism" was sensationalist journalism that distorts, exaggerates, or exploits news to maximize profit. The term came from Joseph Pulitzer's New York World and William Randolph Hearst's New York Journal American, who engaged in sensational reporting during the late 19th and early 20th century, most famously during the Spanish-American War. The term was derived from the color comic strip The Yellow Kid, which appeared in both papers.
Yellow is associated with jaundice, since someone who has that disease turns yellow.
Yellowcake (also known as urania and uranic oxide) is concentrated uranium oxide, obtained through the milling of uranium ore. Yellowcake is used in the preparation of fuel for nuclear reactors and in uranium enrichment, one of the essential steps for creating nuclear weapons.
The March 1967 album by Donovan called Mellow Yellow was very popular among the hippies. The featured song on the album, Mellow Yellow, popularized during the Spring of 1967 a widely believed hoax that it was possible to get high by smoking scrapings from the inside of banana peels, although this rumor was actually started in 1966 by a different musician popular among the hippies, Country Joe McDonald.
In the metaphysics of the New Age Prophetess, Alice A. Bailey, in her system called the Seven Rays which classifies humans into seven different metaphysical personality types, the fourth ray of harmony through conflict is represented by the color yellow. People who have this metaphysical personality type are said to be on the Yellow Ray.
Psychics who claim to be able to observe the aura with their third eye report that someone with a yellow aura is typically someone who is in an occupation requiring intellectual acumen, such as a scientist.
Yellow was also the color of the New Party in the Republic of China (Taiwan), which supports Chinese reunification.
In the United States, a yellow dog Democrat was a Southern voter who consistently voted for Democratic candidates in the late 19th and early 20th centuries because of lingering resentment against the Republicans dating back to the Civil War and Reconstruction period. Today the term refers to a hard-core Democrat, supposedly referring to a person who would vote for a "yellow dog" before voting for a Republican.
The Monster Raving Loony Party (OMRLP) has made use of yellow, along with black, as its primary party colors.
The best-known personage associated with yellow is the current king of Thailand, Bhumibol Adulyadej. Ever since the political crisis of 2005-2006, during the events of the 2006 Thai coup d'état, in honor of the 60th anniversary of his accession to the throne and continuing until his 80th birthday celebration on 5 December 2007, Thailand has been a veritable sea of yellow as the people of Thailand show support for their king.
In Association football (soccer), the referee shows a yellow card to indicate that a player has been officially cautioned.
In American Football, a yellow flag is thrown onto the field by a referee to indicate a penalty.
Originally in Rugby League and then later, also in Rugby Union, the referee shows a yellow card to indicate that a player has been sent to the sin bin.
In auto racing, a yellow flag signals caution. Cars are not allowed to pass one another under a yellow flag.
In cycle racing, the yellow jersey - or maillot jaune - is awarded to the leader in a stage race. The tradition was begun in the Tour de France where the sponsoring L'Auto newspaper (later L'Équipe) was printed on distinctive yellow newsprint.
In some countries, taxicabs are commonly yellow. This practice began in Chicago, where taxi entrepreneur John Hertz painted his taxis yellow based on a University of Chicago study alleging that yellow is the color most easily seen at a distance.
In Canada and the United States, school buses are almost uniformly painted a yellow color (often referred to as "school bus yellow") for purposes of visibility and safety, and British bus operators such as FirstGroup plc are attempting to introduce the concept there.
"Caterpillar yellow" and "high-visibility yellow" are used for highway construction equipment.
In the rules of the road, yellow (called "amber" in Britain) is a traffic light signal warning that the period in which passage is permitted is coming to an end. It is intermediate between green (go) and red (stop). In railway signaling, yellow is often the color for warning, slow down, such as with distant signals.
Several light rail and rapid transit lines on various public transportation have a Yellow Line.
In International maritime signal flags a yellow flag denotes the letter "Q". It also means a ship asserts that she does not need to be Quarantined.