If you stare at the the black + in the center, the moving dot turns to green.
Now, 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'll 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.