Pink Dot Circle Illusion
What to see and do: Stare at the cross in the middle of the picture for 30 seconds. If you are successful, the pink dots will suddenly turn green. After a few more seconds, they will disappear completely. If you follow the green dot around the circle, you will see that it is really gray.
What's happening: This is caused by an effect called an afterimage. When an afterimage occurs and the dots dissapear, your eye overcompensates to fill the color back in with the opposite of the color, which, in this case, is green. While your eyes have been working hard to show pink, the opposite, or green cells, have been resting. When all the colors have to work again, pink doesn't work as hard and the green produces the most because it has been resting.
Credit: This illusion was created by Jeremy L. Hinton and published on the World Wide Web by Michael Bach.