[sahy-uh-noh-bak-teer-ee-uh, sahy-an-oh-]
or blue-green algae

Any of a large group of prokaryotic, mostly photosynthetic organisms. Though classified as bacteria, they resemble the eukaryotic algae in many ways, including some physical characteristics and ecological niches, and were at one time treated as algae. They contain certain pigments, which, with their chlorophyll, often give them a blue-green colour, though many species are actually green, brown, yellow, black, or red. They are common in soil and in both salt and fresh water, and they can grow over a wide range of temperatures, from Antarctic lakes under several metres of ice to Yellowstone National Park's hot springs in the U.S. Cyanobacteria are often among the first species to colonize bare rock and soil. Some are capable of nitrogen fixation; others contain pigments that enable them to produce free oxygen as a by-product of photosynthesis. Under proper conditions (including pollution by nitrogen wastes) they can reproduce explosively, forming dense concentrations called blooms, usually coloured an opaque green. Cyanobacteria played a large role in raising the level of free oxygen in the atmosphere of early Earth.

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Mottled, blue-gray baleen whale (Balaenoptera musculus), also called sulfur-bottom whale because of the yellowish diatoms on some individuals. The largest of all animals, the blue whale reaches a maximum length of about 100 ft (30 m) and a maximum weight of 150 tons (136,000 kg). It is found alone or in small groups in all oceans. In summer it feeds on krill in polar waters, and in winter it moves toward the equator to breed. It was once the most important of the commercially hunted baleen whales, and its populations were greatly reduced. Listed as an endangered species, it is now protected.

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U.S. statute regulating work, commerce, and amusements on Sundays. The name is said to derive from a list of Sabbath regulations published (on blue paper or in blue wrappers) in New Haven, Conn., in 1781. Throughout colonial New England such laws regulated morals and conduct. Most lapsed after the American Revolution, but some, such as prohibitions against the Sunday sale of alcoholic beverages, remain on the books in some areas.

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or blue ground

Dark, heavy, often fragmented igneous rock that may contain diamonds in the rock matrix. Kimberlite is a mica peridotite, an ultrabasic rock type with a complex and often highly altered mineral composition. It occurs in the Kimberley district of South Africa and the Kimberley and Lake Argyle regions of Australia, as well as near Ithaca, N.Y.

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Blue crab (Callinectes sapidus)

Any member of a genus (Callinectes) of decapods, particularly C. sapidus and C. hastatus, common edible crabs of the western Atlantic coast prized as delicacies. Their usual habitats are muddy shores, bays, and estuaries. The blue crab shell, greenish on top and dingy white below, is about 3 in. (15–18 cm) long. The legs are bluish. The chelae, or pincers, are large and somewhat unequal in size, and the fifth pair of legs is flattened for swimming. Blue crabs are scavengers.

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Any member of the widely occurring lepidopteran family Lycaenidae. Adults, sometimes known as gossamer-winged butterflies, are small and delicate, with a wingspan of 0.75–1.5 in. (18–38 mm). Blues are rapid fliers, and most species have iridescent wings. Larvae are short, broad, and sluglike. Some species secrete honeydew, a sweet by-product of digestion that attracts ants, which stroke the larvae with their legs to stimulate honeydew secretion.

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or blue asbestos

Gray-blue to green, highly fibrous (asbestiform) form of the amphibole mineral riebeckite. It has higher tensile strength than chrysotile asbestos. The major commercial source is South Africa, where it occurs in Precambrian banded-iron formations; it is also found in Australia and Bolivia.

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or Blue Ridge Mountains

Section of the Appalachian Mountains, eastern U.S. The range extends southward from Carlisle, Pa., through parts of Maryland, Virginia, North Carolina, and South Carolina to Mt. Oglethorpe in Georgia. The highest peaks are in the Black Mountains of North Carolina; the average elevation is 2,000–4,000 ft (600–1,200 m). The scenic Blue Ridge Parkway, established in 1936 and administered by the National Park Service, runs 469 mi (755 km) along the crest.

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Mountain range, eastern Jamaica. It extends from north of Kingston eastward 30 mi (50 km) to the Caribbean Sea. Its highest point is Blue Mountain Peak, at 7,388 ft (2,252 m). It experiences heavy rain and widely divergent temperatures. Blue Mountain coffee is famous for its excellent quality.

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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). 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.

Etymology and definitions

The modern English word blue 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, but it can refer to other colours. 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 (cyan) was used for dark blue enamel.

As a curiosity, blue is thought to be cognate with blond, blank 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, blank) (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), 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 or cyan). The phrase "feeling blue" is linked also to a custom among many old deepwater sailing ships. If the ship lost the captain or any of the officers during its voyage, she would fly blue flags and have a blue band painted along her entire hull when returning to home port.

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). Blue is commonly used on internet browsers to colour a link that has not been clicked; when a link has been clicked it changes yellow or orange or purple.

In science


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

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

Scientific natural standards for blue

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


  • 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. 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.

Blue in human culture

English language

  • In the English language, blue often represents the human emotion of sadness, e.g. "He was feeling blue".


  • 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.
  • In 1999 Eiffel 65 released the song "Blue (Da Ba Dee)," a hugely popular Eurodance song which peaked at #2 on the Billboard Hot 100 in the United States, and reached #1 in 17 countries.
  • Blue is also the name of an English pop boy band.

National colours




  • 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, 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)". 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. According to several rabbinic sages, blue is the colour of God's Glory. 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. (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.


  • 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.
  • In the early 1960s, the United States Air Force ran a television commercial with this jingle:

They took the blue from the skies
And the pretty girls' eyes
And a touch of Old Glory too;
And gave it to the men who proudly wear the U. S. Air Force Blue!

Variations of blue

Dark blue

Dark blue is a shade of blue.

The name comes from the word "Dark" (which originated from Old English dark, derk, deork; Anglo-Saxon dearc, and Gaelic and Irish dorch, dorcha) and "Blue" (taken from French and originated from the Indo-European root bhlewos).

Medium blue

Displayed at right is the colour medium blue.

Light blue

The web colour light blue is displayed in the colour box at right. Also could be known as, sky blue, baby blue, or angel blue.

The first recorded use of "light blue" as a colour term in English is in the year 1915.

Pigment blue

At right is the color pigment blue. This is the color that is achieved by mixing an equal amount of process cyan (printer's cyan) and process magenta (printer's magenta).

Variations of blue in culture


Law Enforcement



See also


External links

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