Those which depend on the state of our eye, and not those which the object really possesses. Thus, after looking at the bright sun, all objects appear dark; that dark colour is the accidental colour of the bright sun. When, again, we come from a dark room, all objects at first have a yellow tinge. This is especially the case if we wear blue glasses, for a minute or two after we have taken them off.
The accidental colour of red is bluish green, of orange dark blue, of violet yellow, of black white; and the converse.