they can seem like magic
Excerpted from The Power of Persuasion: How We’re Bought and Sold by Robert V. Levine, ©2003:
Matisse, it was said, could create any color in a painting without touching the color itself. All he asked was to control the colors around it. Similarly, look closely at a Van Gogh or a Monet or virtually any other impressionist work and you’ll have a hard time finding an accurately depicted color or clean brush stroke. These paintings are populated by oddities like people with bright orange hands and green faces; with irregular globs of paint that represent flags and trees; and with what appear to be accidental brush drippings that pass off as stars and steeples. Every detail on the canvas, seen in isolation, is inaccurate. But it all looks right when you stand back and take in the whole painting.
In perception, context is everything. Colors and shapes are elastic creatures that change with their surroundings. A black picture frame will make a gray painting look lighter; a white frame turns it darker. Put the same gray painting against a green background and it becomes pink. If you want to see a total color change, place a strong blue up against a red and watch the red turn orange—not orangish, but actual orange. Now vary the size, the shape, or the placement of any of these objects and everything changes again. You don’t have to squint or make an effort to see the changes. If your vision is normal, they can’t be seen any other way. The changes are so dramatic that to the unprepared viewer, they can seem like magic.