1A greyish-blue colour.
A small dark mayfly of the genus Baetis ; an artificial fly made in imitation of it.
3Any of various blue pigments containing iron, especially. Prussian blue.
Of a greyish-blue colour; designating this colour.
Late 17th century; earliest use found in John Dryden (1631–1700), poet, playwright, and critic. From iron + blue.