https://en.m.wikipedia.org/wiki/Blue
The modern English word blue comes from Middle English bleu or blewe, from the Old French bleu, a word of Germanic origin, related to the Old High German word blao.[5] In heraldry, the word azure is used for blue.[6] Different words, such as lapis, cerulean, sky blue, and indigo, are used to describe particular shades of blue.
In Russian and some other languages, there is no single word for blue, but rather different words for light blue (голубой, goluboy) and dark blue (синий, siniy). See Colour term.
Several languages, including Japanese, Thai, Korean, and Lakota Sioux, use the same word to describe blue and green. For example, in Vietnamese the color of both tree leaves and the sky is xanh. In Japanese, the word for blue (青 ao) is often used for colors that English speakers would refer to as green, such as the color of a traffic signal meaning "go". (For more on this subject, see Distinguishing blue from green in language)
Linguistic research indicates that languages do not begin by having a word for the color blue.[7] Color names often developed individually in natural languages, typically beginning with black and white (or dark and light), and then adding red, and only much later – usually as the last main category of color accepted in a language – adding the color blue, probably when blue pigments could be manufactured reliably in the culture using that language.[7]
Blue was a latecomer among colors used in art and decoration, as well as language and literature.[24] Reds, blacks, browns, and ochres are found in cave paintings from the Upper Paleolithic period, but not blue. Blue was also not used for dyeing fabric until long after red, ochre, pink and purple. This is probably due to the perennial difficulty of making good blue dyes and pigments.[25] The earliest known blue dyes were made from plants – woad in Europe, indigo in Asia and Africa, while blue pigments were made from minerals, usually either lapis lazuli or azurite.
Lapis lazuli, a semi-precious stone, has been mined in Afghanistan for more than three thousand years, and was exported to all parts of the ancient world.[26] In Iran and Mesopotamia, it was used to make jewellery and vessels. In Egypt, it was used for the eyebrows on the funeral mask of King Tutankhamun(1341–1323 BC).[27] Importing lapis lazuli by caravan across the desert from Afghanistan to Egypt was very expensive. Beginning in about 2500 BC, the ancient Egyptians began to produce their own blue pigment known as Egyptian blue by grinding silica, lime, copper, and alkalai, and heating it to 800 or 900 °C (1,470 or 1,650 °F). This is considered the first synthetic pigment.[28] Egyptian blue was used to paint wood, papyrus and canvas, and was used to color a glaze to make faience beads, inlays, and pots. It was particularly used in funeral statuary and figurines and in tomb paintings. Blue was considered a beneficial color which would protect the dead against evil in the afterlife. Blue dye was also used to color the cloth in which mummies were wrapped.[29]
In Egypt blue was associated with the sky and with divinity. The Egyptian god Amun could make his skin blue so that he could fly, invisible, across the sky. Blue could also protect against evil; many people around the Mediterranean still wear a blue amulet, representing the eye of God, to protect them from misfortune.[30] Blue glass was manufactured in Mesopotamia and Egypt as early as 2500 BC, using the same copper ingredients as Egyptian blue pigment. They also added cobalt, which produced a deeper blue, the same blue produced in the Middle Ages in the stained glass windows of the cathedrals of Saint-Denis and Chartres.[31] The Ishtar Gate of ancient Babylon (604–562 BC) was decorated with deep blue glazed bricks used as a background for pictures of lions, dragons and aurochs.[32]
The ancient Greeks classified colors by whether they were light or dark, rather than by their hue. The Greek word for dark blue, kyaneos, could also mean dark green, violet, black or brown. The ancient Greek word for a light blue, glaukos, also could mean light green, grey, or yellow.[33] The Greeks imported indigo dye from India, calling it indikon. They used Egyptian blue in the wall paintings of Knossos, in Crete, (2100 BC). It was not one of the four primary colors for Greek painting described by Pliny the Elder (red, yellow, black, and white), but nonetheless it was used as a background color behind the friezes on Greek temples and to color the beards of Greek statues.[34]
The Romans also imported indigo dye, but blue was the color of working class clothing; the nobles and rich wore white, black, red or violet. Blue was considered the color of mourning, and the color of barbarians. Julius Caesar reported that the Celts and Germans dyed their faces blue to frighten their enemies, and tinted their hair blue when they grew old.[35] Nonetheless, the Romans made extensive use of blue for decoration. According to Vitruvius, they made dark blue pigment from indigo, and imported Egyptian blue pigment. The walls of Roman villas in Pompeii had frescoes of brilliant blue skies, and blue pigments were found in the shops of color merchants.[34] The Romans had many different words for varieties of blue, including caeruleus, caesius, glaucus, cyaneus, lividus, venetus, aerius, and ferreus, but two words, both of foreign origin, became the most enduring; blavus, from the Germanic word blau, which eventually became bleu or blue; and azureus, from the Arabic word lazaward, which became azure.[36]