colour: [13] The Old English words for ‘colour’ were hīw ‘hue’ and blēo, but from the 13th century onwards they were gradually replaced by Old French colour. This came from Latin color, which appears to have come ultimately from an Indo-European base *kel- ‘hide’ (source also of apocalypse, cell, clandestine, conceal, and occult).
This suggests that its original underlying meaning was ‘outward appearance, hiding what is inside’, a supposition supported by the long history of such senses of English colour as ‘outward (deceptive) appearance’ and ‘(specious) plausibility’ (as in ‘lend colour to a notion’). => apocalypse, cell, conceal, hell, occult
