Focus on the yellow stripe in the middle of the fish for 15-30 seconds. Try not to blink. Then move your mouse so that the cursor moves into the picture. This will cause a fishbowl to appear. Do you see the fish in the bowl? What color is the fish?
What's Happening: in the retina of your eyes, there are 3 types of color receptors (cones) that are most sensitive to either red, blue or green. When you stare at a particular color for too long, these receptors get "tired" or "fatigued." When you then look at the white background, the receptors that are tired do not work as well. Therefore, the information from all of the different color receptors is not in balance and you see the color "afterimages." You can see that you vision quickly returns to normal.