Do colors have opposites?

Do colors have opposites?
Here's a little experiment for you to try. Find yourself a piece of paper in a solid bright color. Now find a white wall. Place a chair about 5 feet from the wall. Now tape the paper to the wall at what would be eye level when you are sitting in the chair.

Now sit down and stare at the paper for about fifteen seconds. Quickly look away from the paper to a blank part of the wall and let your eyes settle. What you will see is an image of the paper in negative. The color you now see is the opposite of the color that the paper is.

Google COLOR THEORY and choose most any link. Or go to http://www.colormatters.com/colortheory.html and check out the color wheels on that page for m ore information.