Blue
— Spectral coordinates —
Wavelength		450–490 nm
Frequency		~670–610 THz
— Common connotations —
Ice, water, sky, sadness, winter, police, royalty, Hanukkah, boys, cold, calm, magic, trueness, conservatism (universally), liberalism (US), and capitalism
— Colour coordinates —
Hex triplet		#0000FF
sRGBB	(r, g, b)	(0, 0, 255)
HSV	(h, s, v)	(240°, 100%, 100%)
Source		HTML/CSS[1]
B: Normalized to [0–255] (byte)

The sky and water often appear blue.

Blue Turkish Tiles

Blue is a colour, the perception of which is evoked by light having a spectrum dominated by energy with a wavelength of roughly 450–490 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) where blue was considered a primary colour, its complementary colour is considered to be orange (based on the Munsell colour wheel).^[2]

In Modern English, "blue" is one of the basic colour terms, and one of the seven spectral colours, intermediate between violet (purple) and cyan. It comprises a considerable number of identifiable subcategories that can be identified with descriptive terms like navy blue (a dark blue), cyan blue (or "blue-green", on the boundary to the green range), or sky blue (azure).

The word itself was loaned into Middle English from the Old French word bleu, blo "pale, pallid, discoloured; blue, blue-grey", itself from an Old Frankish *blao.

Etymology [link]

The modern English word blue comes from Middle English bleu or blewe, from Old French bleu, bleve, blöe, a word of Germanic origin (Frankish or possibly Old High German blāo, "pale, wan, blue-grey").

Bleu replaced Old English blāw "blue" and blǣwen "light blue". The root of all these variations is Proto-Germanic blǣwaz, from Proto-Indo-European *bhlāw-, *bhlēw- "light-coloured, yellow, grey, blue", from *bhel- "to shine, be light or bright", also the root of Old Norse blār and the modern Icelandic blár, and the Scandinavian word blå, which can also refer to other non blue colours. A Scots and Scottish English word for "blue-grey" is blae, from the Middle English bla ("dark blue", from Old Norse blār). Also related is the English word blee meaning "colour, complexion".

The same Indo-European root also underlies the English words black, blond, and also Latin flavus ("yellow"; see flavescent and flavine), Greek phalos (white), French blanc (white, blank) (borrowed from Old Frankish), Russian белый, belyi ("white," see beluga), and Welsh blawr (grey).

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).

In science [link]

Pigments and dyes [link]

Traditionally, blue has been considered a primary colour in painting, with the secondary colour orange as its complement.

Blue pigments include azurite (Cu₃(CO₃)₂(OH)₂), ultramarine (Na_8-10Al₆Si₆O₂₄S_2-4), cerulean blue (primarily cobalt (II) stanate: Co₂SnO₄), cobalt blue (cobalt(II) aluminate: CoAl₂O₄), and Prussian blue (milori blue: primarily Fe₇(CN)₁₈).

Traditionally natural dyes such as woad and true indigo were used to produce indigo dye used to colour fabrics blue or indigo. These have now largely been replaced by synthetic dyes.

Scientific natural standards for blue [link]

• Emission spectrum of Cu²⁺
• Electronic spectrum of aqua-ions Cu(H₂O)2+
  6

Animals [link]

• When an animal's coat is described as "blue", it usually 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, some horse coat colours and rabbit coat colours. Some animals, such as giraffes and lizards, also have blue tongues.

Lasers [link]

Lasers emitting in the blue region of the spectrum became widely available to the public in 2010 with the release of inexpensive high-powered 445-447 nm Laser diode technology.^[3] Previously the blue wavelengths were accessible only through DPSS which are comparatively expensive and inefficient, however these technologies are still widely used by the scientific community for applications including Optogenetics, Raman spectroscopy, and Particle image velocimetry, due to their superior beam quality.^[4] Blue Gas lasers are also still commonly used for Holography, DNA sequencing, Optical pumping, and other scientific and medical applications.

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  Blueberries

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  Lactarius indigo is one of only a few blue-coloured mushrooms.

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  Dendrobates azureus

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  Blue Jay

In culture [link]

Symbolic language [link]

• In the English language, blue often represents the human emotion of sadness, for example, "He was feeling blue". In German, on the other hand, to be "blue" (blau sein) is to be drunk. This derives from the ancient use of urine (which is produced copiously by the human body after drinking alcohol) in dyeing cloth blue with woad or indigo.^[5] It may also be in relation to rain, which is usually regarded as a trigger of depressive emotions.^[6]
• Conversely blue, a very popular colour^[7] can represent happiness and optimism^[8] as days with clearer, blue skies tend to be considered times where these emotions are more easily expressed. Many artistic contributions have been made referencing clear days with blue skies as part of the happiness or as a symbolism of the happiness the artist felt, such as Tony Bennett's Put on a Happy Face.^[9]
• Blue is commonly used in the Western hemisphere to symbolize the male gender in contrast to pink used for females, although in the early 1900s, blue was the colour for girls (as it had traditionally been the colour of the Virgin Mary in Western Art) and pink was for boys (as it was akin to the colour red, considered a masculine colour).^[10]

National colours [link]

Flag of Greece

Coat of Arms symbol of Israel

• Azzurro, a light blue, is the national colour of Italy (from the livery colour of the former reigning family, the House of Savoy).
• Blue is the national sports colour for India, as it denotes secularism.^{[citation needed]}
• Blue is the national colour used on flags of several countries surrounded by seas or oceans such as Australia and Europe, though not necessarily with this interpretation in mind.
• Blue and white are the national colours of Scotland, Argentina, El Salvador, Finland, Greece, Guatemala, Honduras, Israel, Micronesia, Nicaragua and Somalia, are the ancient national colours of Portugal and are the colours of the United Nations.
• Blue, white and yellow are the national colours of Bosnia and Herzegovina, Kosovo and Uruguay.
• Blue, white and green are the national colours of Sierra Leone.
• Blue, white and black are the national colours of Estonia.^[11]
• Blue and yellow are the national colours of Barbados, Kazakhstan, Palau, Sweden, and Ukraine.
• Blue, yellow and green are the national colours of Brazil, Gabon, and Rwanda.
• Blue, yellow and red are the national colours of Chad, Colombia, Ecuador, Moldova, Romania, and Venezuela.
• Blue and red are the national colours of Haiti and Liechtenstein.
• Blue, red and white are the national colours of Cambodia, Costa Rica, Chile, Croatia, Cuba, the Czech Republic, the Dominican Republic, France, Iceland, North Korea, Laos, Liberia, Luxembourg, Nepal, the Netherlands, New Zealand, Norway, Panama, Paraguay, Puerto Rico, Russia, Samoa, Serbia, Slovakia, Slovenia, Thailand, the United Kingdom, and the United States.

Mysticism [link]

• In Hinduism, blue is used to symbolically represent the fifth, throat chakra (Vishuddha).^[12]

Politics [link]

This unreferenced section requires citations to ensure verifiability.

• The Blue House is the residence of the President of South Korea.^[13]
• 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, blues 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.
• The blueshirts was a quasi-fascist political organisation active in Ireland during the 1930s (the name comes from the fact that St. Patrick's Blue is one of the traditional colours of Ireland).
• Blue is the colour of the Conservative Party in Britain and Conservative Party of Canada. Television coverage in the United States since the 2000 presidential election has made it fashionable to link the Democratic Party to "blue" and the Republican Party to "red" (especially in reference to "red states and blue states").^[14] In Brazil, blue states are the ones in which the Social Democratic Party has the majority, in opposition to the Workers' Party, usually represented by red.
• A blue law is a type of law, typically found in the United States and Canada, designed to enforce religious standards, particularly the observance of Sunday as a day of worship or rest, and a restriction on Sunday shopping. The word blue was used in the 17th century as a disparaging reference to rigid moral codes and those who observed them, particularly in blue-stocking, a reference to Oliver Cromwell's supporters in the parliament of 1653.
• Blue is associated with numerous centre-right liberal political parties in Europe, Including the People's Party for Freedom and Democracy (Netherlands), the Reformist Movement and Open VLD (Belgium), the Democratic Party (Luxembourg), Liberal Party (Denmark) and Liberal People's Party (Sweden).
• Blue is the colour of, and associated with, the New Progressive Party of Puerto Rico.

Religion [link]

Blue coloured Lapis lazuli semi-precious stones are prized among Muslim Cultures in the Caucasus, Central Asia and Mehrgarh.

Blue stripes on a traditional Jewish tallit.

• Blue is associated in Christianity generally and Catholicism in particular, with the Virgin Mary.^[15][16][17]
• Blue in Hinduism: Many of the gods are depicted as having blue-coloured skin, particularly those associated with Vishnu, who is said to be the Preserver of the world and thus intimately connected to water. Krishna and Ram, Vishnu's avatars, are usually blue. Shiva, the Destroyer, is also depicted in light blue tones and is called neela kantha, or blue-throated, for having swallowed poison in an attempt to turn the tide of a battle between the gods and demons in the gods' favour.
• Blue in Judaism: In the Torah,^[18] 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)".^[19] 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.^[20] According to several rabbinic sages, blue is the colour of God's Glory.^[21] 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.^[22] (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.^[23]
• Blue in Islam: the colour blue is mentioned in the Quran: In verse 20:102 and is represented by the word: زرق zurq (plural of azraq, "blue"). Blue amulets made of lapis lazuli are commonly utilised to symbolise luck in some Muslim cultures. The colour blue also represents the values of liberty among Bosniaks.

Symbolism [link]

• 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.^[24]

Sports [link]

Many sporting teams make blue their official colour, or use it as detail on kit of a different colour. In addition, the colour is present on the logos of many sports associations.

Association football [link]

In international association football, blue is a common colour on kits, as a majority of nations wear the colours of their national flag. A notable exception is four-time FIFA World Cup winners Italy, who wear a blue kit based on the Azzuro Savoia (Savoy blue) of the royal House of Savoy which unified the Italian states.^[25] The team themselves are known as Gli Azzurri (the Blues). Another World Cup winning nation with a blue shirt is France, who are known as Les Bleus (the Blues). Two neighbouring countries with two World Cup victories each, Argentina and Uruguay wear a light blue shirt, the former with white stripes. Uruguay are known as the La Celeste, Spanish for 'the sky blue one', while Argentina are known as Los Albicelestes, Spanish for 'the sky blue and whites'.^[26]

Football clubs which have won the European Cup or Champions League and wear blue include FC Barcelona of Spain (red and blue stripes), FC Internazionale Milano of Italy (blue and black stripes) and FC Porto of Portugal (blue and white stripes). Another European Cup-winning club, Aston Villa of England, wear light blue detailing on a mostly claret shirt, often as the colour of the sleeves.^[27] Clubs which have won the Copa Libertadores, a tournament for South American clubs, and wear blue include six-time winners Boca Juniors of Buenos Aires, Argentina. They wear a blue shirt with a yellow band across.

Blue features on the logo of football's governing body FIFA, as well as featuring highly in the design of their website.^[28] The European governing body of football, UEFA, uses two tones of blue to create a map of Europe in the centre of their logo. The Asian Football Confederation, Oceania Football Confederation and CONCACAF (the governing body of football in North and Central America and the Caribbean) use blue text on their logos.

North American sporting leagues [link]

In Major League Baseball, the premier baseball league in the United States of America and Canada, blue is one of the three colours, along with white and red, on the league's official logo. A team from Toronto, Ontario, are the Blue Jays. The Los Angeles Dodgers use blue prominently on their uniforms and the phrase "Dodger Blue" is may be said to describe Dodger fans' "blood". The Texas Rangers also use Blue prominently on their uniforms and logo.

The National Basketball Association, the premier basketball league in the United States and Canada, also has blue as one of the colours on their logo, along with red and white also, as does its female equivalent, the WNBA. The Sacramento Monarchs of the WNBA wear blue. Former NBA player Theodore Edwards was nicknamed "Blue". The only NBA team to wear blue as first choice are the Charlotte Bobcats, however blue is a common away colour for many other franchises.

The National Football League, the premier American football league in the United States, also uses blue as one of three colours, along with white and red, on their official logo. The Seattle Seahawks, New York Giants, Buffalo Bills, and Detroit Lions feature blue prominently on their uniforms.

The National Hockey League, the premier Ice hockey league in Canada and the United States, does not use blue on its official logo. However, a club in the league from St. Louis, Missouri is named the Blues.

• Italia v Francia Mondiale 1978.jpg

  The Italian national football team wear blue in honour of the royal House of Savoy which unified the country.

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  The New Orleans Hornets, a National Basketball Association franchise from New Orleans, Louisiana, United States, wear blue as an away colour.

Variations [link]

See also [link]

• Blue Flag (disambiguation)
• Blue movie (disambiguation)
• Blue ribbon
• Blue Screen of Death
• Distinguishing "blue" from "green" in language
• Engineer's blue
• List of colours
• Non-photo blue
• St. Patrick's Blue
• Shades of blue
• Turquoise

References [link]

External links [link]

Look up blue in Wiktionary, the free dictionary.

Wikimedia Commons has media related to: blue