Remarks on Color

Why do people find it intuitive to describe this kind of very powerful simultaneous color-contrast effect as an "illusion"? After all, the look of a color against a white background depends just as much on its background as the look of the spirals in the example depend on their background.

Here are some more simultaneous color contrast "illusions" from the same source as the first one.

Metamers seem to present a problem for physicalist theories of color. Make some yourself.

Another blow to the reliability of the inference from "I can't imagine the possibility of p" to "p is impossible": it might be possible for something to be simultaneously green and red all over.

Take a color discrimination test.