"After-images occur when the eyes had a concentrated burst of a single colour for a period of time. It triggers the optic nerve to create a brief flash of its complementary opposite, so fleeting it hardly ever registers. Ever wondered why surgical scrubs and operating theatre textiles are blue-green? It's the complementary color of blood red and, because the optic nerve recognizes the complementary colour when they look up, it prevents the surgeons getting an after-image when they look away from the open wound." from "Chromatic Scale" in the newest issue of Selvedge Color is crazy!