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 non blue 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 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) (borrowed 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).- Wikipedia
