From Latin 'color,' probably from PIE *kel- (to cover) — colour was originally 'that which covers a surface.'
The property of objects that produces different sensations on the eye as a result of the way they reflect or emit light; a particular variety of this, such as red, blue, or green.
From Middle English 'colour,' from Anglo-French 'culur' and Old French 'color,' from Latin 'color' (colour, hue, complexion, appearance), possibly from an older form *colos, related to 'cēlāre' (to hide, to conceal), from PIE *ḱel- (to cover, to conceal). If this etymology is correct, colour was originally 'that which covers' — a surface's outer covering or appearance, its visible disguise. The same PIE root gave English 'conceal,' 'cell,' 'helmet,' and 'hell.' Key roots: *ḱel- (Proto-Indo-European: "to cover, to conceal").
If the standard etymology is correct, 'colour' and 'conceal' share the same PIE root *ḱel- (to cover). Colour was originally 'the covering' — the visible surface that hides what is underneath. Every colour is, in this ancient view, a form of concealment: the outer face that objects present to the world while hiding their inner nature.