Try covering your right eye and looking at the black and white star. Now move your head slowly towards the screen, and eventually the coloured star on the left will magically vanish.
Blind spots are to do with the design of our eyes. The cells in the retina, at the back of the eye, collect light through our lens of all that?s in front of us. In a certain area where our nerves connect the eye to the brain, light does not grow. Light hitting this area of nerves is not picked up, and a blind spot is the result.
Archive of illusions.org: