Color contrast: multiple cues

Moving the mask makes it apparent that statistical information about probable sources strongly affects color, as well as lightness and/or brightness. Here, two spectrally identical patches (indicated with a dot) appear gray-green when viewed in isolation, but look reddish and bluish, respectively, when viewed in the context of empirical information that makes different surfaces under different chromatic illuminants a highly likely source of the stimulus.

(Image by Beau Lotto - www.lottolab.org)