If your eyes follow the movement of the rotating pink dot, the dots will remain only one color, pink. However if you stare at the black " +" in the centre, the moving dot turns to green. Now, concentrate on the black " + " in the centre of the picture. After a short period, all the pink dots will slowly disappear, and you will only see only a single 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.