Whats coming out of the square

Don’t worry, there aren’t any ghosts coming out of the square. Just watch, and analyze as to why, the illusion happens.  
If you continue to focus on the  cross  in the center of the image you will notice that ..     

 

 click at the image

 
 
  
the circle of violet circles will soon  DISAPPEAR completely ..  and you will see only the green spot (which is actually violet)