If your eyes follow the movement of the rotating pink dot, you will only see one color, pink.
If you stare at the black + in the center, the moving dot turns to green.
If you concentrate on the black + in the center of the picture, after a short period of time, all the pink dots will slowly disappear, and you will only see a green dot rotating.
It's amazing how our brain works. There really is no green dot, and the pink ones really don't disappear. This should be proof enough; we don't always see what we think we see.
Source:
Patmedia