Accidental Colours are the imaginary complementary colours (not caused by light, but due to subjective sensation; see COLOUR) which are seen when, after looking fixedly at a bright-coloured object, the eye is turned to a white or light-coloured surface. If the object was red, the accidental colour will be green. Blue corresponds in like manner to yellow.
Accidental Colours
Chambers's Encyclopaedia, Volume 1: A to Beaufort, p. 30
Source scan(s): p. 0043