Wiktionary
unblue
(context rare outside philosophy English) Not blue. v
1 (lb en intransitive rare chiefly poetic) To cease being blue. 2 (lb en transitive rare chiefly poetic) To cause (something) to cease being blue; to make (something) not blue.
Usage examples of "unblue".
Suddenly, impossibly, there was a flash of unwhite, unblue, a flicker of color in the black.