Take a good look at the two versions of the head and hands from Edvard Munch's "Scream" below ... what color do each of these look to you? Purple and orange? Red and orange? Something else? What if I told you that both Munch "Screams" are red? How is that possible?
Can you force your eye to ignore the vertical stripes and just look at the Munch "Scream" face? What makes this tricky - and what forces the illusion of different colors - is the fact that the blue stripes sit on top of the Munch Scream face at left, and the yellow stripes sit on top of the Munch Scream face at right. What your eye is most-likely doing is making a partial mix of the colors in both cases - at left, your eye is mixing the red Scream with blue stripes to make purple, and at right, your eye is mixing the red Scream with yellow stripes to make orange.
It's a little easier to see what I'm talking about if I pull the Munch Scream heads up above the stripes, as you can see in the picture below. The idea that our perception of a color is affected by its surrounding colors is something called "The Bezold Effect," named after its discoverer, Wilhelm von Bezold (1837–1907). He recognized this effect when he was designing rugs and realized that the same design could have a totally different appearance by changing just one color, which then affected the appearance of the other still-same colors. In our Munch Scream example, the one color change is putting the yellow stripes on top of the red face rather than repeating the blue stripes on top.
A similar visual trick regarding perception of color is called "The Munker-White Illusion," which is shown below left. The color of gray in column A and column B may look totally different, but in fact they are the same, which is illustrated in the version below right. The visual trick here works the same way - below left, having the black horizontal bands on top of the gray column A makes it look dark by association, where the same gray column B looks lighter because the white stripes sit on top. When I create some white space and don't let the colors overlap (below right), then one can see much more clearly that the gray columns A and B are the same.
Just for fun, I thought I'd create another example where making one change and taking something out of it's original context can change the appearance - or in this case - the perception of what is happening. Using Munch's Scream as an example again, we have the Screamer in his original context, in Munch's 1893 painting, below left. Art historians have said that Munch's figure symbolizes the anxiety of modern man. But if we take the Screamer off of this bridge and away from the tormented sky, and place him in Picasso's studio (below right), all of a sudden the scream becomes an act of surprise and joy, as Picasso has decided to give him an artwork as a gift.