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Blue
— Colour coordinates —
Hex triplet		#0000FF
sRGBB	(r, g, b)	(0, 0, 255)
Source		HTML/CSS[1]
B: Normalized to [0–255] (byte)

Blue is a colour, the perception of which is evoked by light having a spectrum dominated by energy with a wavelength of roughly 440–490 nm. It is considered one of the additive primary colours. On the HSV Colour Wheel, the complement of blue is yellow; that is, a colour corresponding to an equal mixture of red and green light. On a colour wheel based on traditional colour theory (RYB), the complementary colour to blue is considered to be orange (based on the Munsell colour wheel).^[2]

The English language commonly uses "blue" to refer to any colour from navy blue to cyan. The word itself is derived from the Old French word bleu. The term may also refer to the human emotion of sadness, e.g. "He was feeling blue". The Blues is a form of music that is inclusive of the blue notes and has a 12 note scale.(See "Music" below.)

Contents 1 Blue in the RGB system 2 Etymology and definitions 3 In science 3.1 Pigments 3.2 Scientific natural standards for blue 3.3 Animals 4 Blue in human culture 4.1 Ethnography 4.2 Gangs 4.3 Medicine 4.4 Music 4.5 National colours 4.6 Mysticism 4.7 Politics 4.8 Recording media 4.9 Religion 4.10 Sexuality 4.11 Sociology 4.12 Symbolism 5 See also 6 References 7 External links

In the RGB colour system, colours are formed by mixing a red, a green and a blue colour. When talking about RGB, therefore, some people use blue to mean that specific blue, which varies in shade according to the device used to display the RGB colour. Absolute colour spaces based on RGB, such as sRGB, define an exact colour for this blue, which may differ from the actual blue used in a particular computer monitor.

Main article: Colour name

The modern English word blue (German:blau) comes from the Middle English, bleu or blwe, which came from an Old French word bleu of Germanic origin (Frankish or possibly Old High German blao, "shining"). Bleu replaced Old English blaw. The root of these variations was the Proto-Germanic blæwaz, which was also the root of the Old Norse word bla and the modern Icelandic blár, and the Scandinavian word blå. It can also be green or orange occasionally (blue). A Scots and Scottish English word for "blue-grey" is blae, from the Middle English bla ("dark blue," from the Old English blæd). Ancient Greek lacked a word for colour blue and Homer called the colour of the sea "wine dark", except that the word kyanos was used for dark blue enamel.

As a curiosity, blue is thought to be cognate with blond and black through the Germanic word. Through a Proto-Indo-European root, it is also linked with Latin flavus ("yellow"; see flavescent and flavine), with Greek phalos (white), French blanc (white) (loaned from Old Frankish), and with Russian белый, belyi ("white," see beluga), and Welsh blawr (grey) all of which derive (according to the American Heritage Dictionary) from the Proto-Indo-European root *bhel- meaning "to shine, flash or burn", (more specifically the word bhle-was, which meant light coloured, blue, blond, or yellow), from whence came the names of various bright colours, and that of colour black from a derivation meaning "burnt" (other words derived from the root bhel- include bleach, bleak, blind, blink, blank, blush, blaze, flame, fulminate, flagrant and phlegm).

In the English language, blue may refer to the feeling of sadness. "He was feeling blue". This is because blue was related to rain, or storms, and in Greek mythology, the god Zeus would make rain when he was sad (crying), and a storm when he was angry. Kyanos was a name used in Ancient Greek to refer to dark blue tile (in English it means blue-green).^[3]

Many languages do not have separate terms for blue and or green, instead using a cover term for both (when the issue is discussed in linguistics, this cover term is sometimes called grue in English).

Traditionally, blue has been considered a primary colour in painting, with the secondary colour orange as its complement.^{[citation needed]}

Blue pigments include azurite, ultramarine, cerulean blue, cobalt blue, and Prussian blue (milori blue).

• Emission spectrum of Cu²⁺
• Electronic spectrum of aqua-ions Cu(H₂O)₅²⁺

• When an animal's coat is described as "blue", it refers to a shade of grey that takes on a bluish tint, a diluted variant of a pure black coat.^{[citation needed]} This designation is used for a variety of animals, including dog coats, some rat coats, cat coats, some chicken breeds, and some horse coat colours.

• For reasons that are not entirely clear, the colour blue has traditionally been taken to represent the ancient Turkic race.^{[citation needed]}

• Blue is the colour claimed by the street gangs Crips and Sureños.^{[citation needed]}

• A Code Blue is declared in emergency medical situations to indicate imminent loss of life when a patient has lost heartbeat and ceased respiration.^{[citation needed]}

• The blues is a style of music originated by African Americans. Contrary to popular belief it is not called Blues because its lyrics are depressing but because its scale is inclusive of the "dark notes" or blue notes.

• Blue and yellow are the national colours of Sweden, Kazakhstan, and Ukraine, and along with green, of Brazil, and along with red, of Colombia, Venezuela, Ecuador, Chad, Romania, and Moldova.

• Blue and white are the national colours of Somalia, Finland, Greece, Israel, Scotland, El Salvador, and Honduras.^{[citation needed]}

• Red and blue are the national colours of Liechtenstein and Haiti, and along with white, The United States, the United Kingdom, France, Luxembourg, Norway, the Czech Republic, Slovakia, the Netherlands, Costa Rica, Serbia, Croatia, Paraguay, Iceland, Panama, Russia, Cuba, Chile, Thailand, Dominican Republic, Puerto Rico, Liberia, Nepal, Slovenia.^{[citation needed]}

• Azzuro, a light blue, is the national colour of Italy (from the livery colour of the former reigning family, the House of Savoy).^{[citation needed]}

• 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 Second Ray of Love/Wisdom is represented by the colour blue. People who have this metaphysical personality type are said to be on the Blue Ray.^{[citation needed]}

• The colour blue or azure is used to symbolically represent the fifth (Vishuddha) chakra.^{[citation needed]}

• Psychics who claim to be able to observe the aura with their third eye report that someone with a blue aura is a person who is oriented toward spirituality.^[4] People with blue auras are said to be in interested in social service work and to be in occupations such as social worker, counselor, teacher, writer, and psychologist.^[5]

Main article: Political colour

This section does not cite any references or sources. Please improve this section by adding citations to reliable sources. Unverifiable material may be challenged and removed. (October 2007)

• Blue has been associated with a variety of political positions, often differentiated from communist red or anarchist black. During the revolt in the Vendée against the French revolution, blue stood for the revolutionary forces, and white for the counter-revolutionaries. Later movements like the Breton blues used the colour to signify allegiance to the ideals of the revolution.^{[citation needed]}

• In the United Kingdom blue is the colour of the Conservative Party. In the United States, however, it has become fashionable since the 2000 Presidential Election to refer to the Democratic Party as "blue" and the Republican Party as "red", particularly as in reference to "red states and blue states".

• The Blue Dog Democrats are a group of conservative Democrats in the United States House of Representatives.^{[citation needed]}

• A Blu-ray Disc is a high-density optical disc formatted for the storage of digital media, including high-definition video.^{[citation needed]}

• Blue plays a symbolic role in a number of world religions. Because blue is the colour of the sky and sea, it has often symbolized divinity,^{[citation needed]} as well as height and depth. It can also represent equilibrium, since its hue suggests a shade midway between white and black, day and night. To the ancient Egyptians, blue was the colour of truth.^{[citation needed]}

• Blue in Christianity: The inside of the open dome in Eastern Christian Churches is painted blue to give the impression of looking up into the heavens.^{[citation needed]} Blue is also the colour Mary wears in iconography. During the European Renaissance, artists began painting Hell and specifically the Devil blue to convey the coldness of being distant from God. This is possibly inspired by Dante's Hell in the Divine Comedy, in which Satan is depicted as living in eternal ice at the centre of Earth. Blue also represents the deadly sin of Lust.^{[citation needed]}

• Blue in Hinduism: In the Hindu faith, persons of a transcendental, or divine nature are displayed as being blue in colour to indicate their dark complexion. The deity Krishna is probably the most famous of this type of depiction within Hindu art. Lord Shiva's neck has blue colour to show that the poison he took to save the world from destruction is still staying in his throat.^{[citation needed]}

• Blue in Judaism: In the Torah, the Israelites were commanded to put fringes, tzitzit, on the corners of their garments, and to weave within these fringes a "twisted thread of blue (tekhelet)".^[6] In ancient days, this blue thread was made from a dye extracted from a Mediterranean snail called the hilazon. Maimonides claimed that this blue was the colour of “the clear noonday sky”; Rashi, the colour of the evening sky.^[7] According to several rabbinic sages, blue is the colour of God’s Glory.^[8] Staring at this colour aids in mediation, bringing us a glimpse of the “pavement of sapphire, like the very sky for purity”, which is a likeness of the Throne of God.^[9] (The Hebrew word for glory. Many items in the Mishkan, the portable sanctuary in the wilderness, such as the menorah, many of the vessels, and the Ark of the Covenant, were covered with blue cloth when transported from place to place.^[10]

• Blue movie is a term used for a pornographic film because early pornographic films in black and white were often shot on inferior grade film which made them look bluish.^{[citation needed]}
• In the bandana code of the gay leather subculture, wearing a Medium blue bandana means one is into the fetish of having sex while (at least initially) wearing a police uniform.^{[citation needed]}

• Blue may denote the working class, derived from the traditional colour of factory uniforms. Blue-collar workers are industrial workers and are often contrasted with white-collar office workers.^{[citation needed]} However, in contrast to "blue collar", the phrase "blue blood" is used to mean "from an aristocratic background", because pale, untanned skin – historically, a sign of nobility – allows blue-tinged veins to show through.^{[citation needed]}

• In many South Pacific countries, the colour blue was often associated with scabies. In the early 1800s, as a result of the rural nature in such countries many wearing the colour blue were often eaten to cleanse the gene pool from the infected. Now, more recently, wearing blue is considered a mark of shame in such poor communities because of its scabies associated heritage.^{[citation needed]}

• Several vocations are associated with blue. Law enforcement, and uniformed police, often wear blue uniforms and have become associated with the colour, as seen in phrases such as "boys in blue", "thin blue line", "blue meanie", "blue wall" and NYPD Blue.^{[citation needed]}

• Blue often denotes injury, such as in the phrase "black and blue", since it is the colour of a bruise. Blue is also used as a word to denote a sad or melancholy state, as in depression, or simply a state of deep contemplation.^{[citation needed]} However, the phrase "blue skies", referring to sunny weather, implies cheerfulness. Symbolically, blue is associated with that state, such as the term blue period to describe Pablo Picasso's work from 1901 to 1904.^{[citation needed]}

• Blue is associated with water; on coloured maps, oceans, lakes, and streams usually appear blue.^{[citation needed]}

• Light blue is often associated with the cold. When with white, blue is associated with ice and snow; and by extension, winter.^{[citation needed]}

• Blue can be associated with France, Quebec and the French Language. The term Les Bleus is often used in a sporting context. In all but motor sports, the Italian colour is light blue, and Italian athletes are called Azzurri.^{[citation needed]}

• Gradients of Blue and other smooth, relaxing visual techniques incorporating Blue are considered calming and soothing.^{[citation needed]}

• Blue is often a colour used to symbolize honesty and trustworthiness. Connected to this, blue traditionally is associated with the Christian virtue faith.^{[citation needed]} Hence, it may also mean naivité, being "blue-eyed". In Scandinavia this expression is used for people who are easily tricked or cheated, and in Japanese the word "aoi", meaning "blue", also indicates innocence and inexperience. The German word for blue is used for "drunk" e.g. "Ich bin blau" – "I'm drunk".^{[citation needed]}

• Blue is associated with the eastern direction in traditional East Asian cosmology.^{[citation needed]}

• In Thailand, Blue is associated with Friday on the Thai solar calendar. Anyone may wear blue on Fridays and anyone born on a Friday may adopt blue as their colour. The Thai language, however, is one that has had trouble distinguishing blue from green. The default word for Blue was recently สีน้ำเงิน literally, the colour of silver, a poetical reference to the silvery sheen of the deep blue sea. It now means Navy Blue, and the default word is now สีฟ้า literally, the colour of the sky.^[11]

• Blue flag
• Blue movie
• Turquoise
• Distinguishing "blue" from "green" in language
• Engineer's blue
• Lapis lazuli, a blue stone
• List of colours
• Three Colors: Blue, a movie

• All About the Colour Blue

v • d • e The Electromagnetic Spectrum
(Sorted by wavelength, short to long) Gamma ray • X-ray • Ultraviolet • Visible spectrum • Infrared • Terahertz radiation • Microwave • Radio waves
Visible (optical) spectrum	Violet • Blue • Green • Yellow • Orange • Red
Microwave spectrum	W band • V band • Ka band • K band • Ku band • X band • C band • S band • L band
Radio spectrum	EHF • SHF • UHF • VHF • HF • MF • LF • VLF • ULF • SLF • ELF
Wavelength designations	Microwave • Shortwave • Mediumwave • Longwave

Web colours	black	gray	silver	white	red	maroon	purple	fuchsia	green	lime	olive	yellow	orange	blue	navy	teal	aqua

v • d • e				Shades of blue
Air Force blue	Alice blue	Azure	Baby blue	Blue	Cerulean	Cerulean blue	Cobalt blue	Columbia blue	Cornflower blue	Dark blue
Denim	Dodger blue	Egyptian blue	Electric blue	Han Purple	Indigo	International Klein Blue	Light blue	Maya Blue	Midnight blue	Navy blue
Periwinkle	Persian blue	Powder blue	Prussian blue	Royal blue	Sapphire	Sky blue	Steel blue	Ultramarine