a fascinating TED talk about color ... it's not as simple as you might think!
pt1 http://www.youtube.com/watch?v=YPlB20a0CQw
pt2 http://www.youtube.com/watch?v=VkEcD9AFLRs
Heh, I could have told you that! One of my favourite examples of colour theory is a shape casting a shadow on a checkerboard surface, people don't believe the dark squares are the same colour as the light squares.
In fact with some playing around you can get people to see gradients and all kinds of things with the right colour combinations.
If I find the example I'm thinking about I'll post it! :D
wow this is deep stuff "the light that falls on your eyes IS LITERALLY MEANINGLESS, because it could mean ANYTHING" ... this video reminds us why CONTEXT is critical for our brain to make sense out of sensory stimuli (not just visual). Check out 5:35 and actually do the 30 second staring at the top dot, amazing how vivid the effect is!
even more amazing is the "center on top vs. center on the left" color comparison @ 8minutes -- they look SO different. The skeptic in me had to check it myself, I copied into MSpaint and cut away most of the CONTEXT and voila! same color!
(http://img580.imageshack.us/img580/9360/centerstopvsleft.png)