Not mixed or adulterated; clean, clear, refined; spec. (a) not mixed with any other substance or material; free from admixture or adulteration…

Esp. of a colour: bright, pure, vivid, brilliant. Of a person's complexion, etc.: bright, glowing, healthy.

Of water: clean, pure; (of another liquid) clear, not cloudy. Formerly also of colour: †bright, pure, not dull or muddy (obsolete).

Hence as a poetic epithet of colour: Pure, clear, bright. Also (cf. A. 2b), Quiet, sober.