I love this! In third grade I did a science project on basic optical illusions and color processing in our vision similar to some of these...
Have you seen the black orange and green US flag? If you stare at it for a minute, then stare at blank white space, you will see its negative as the standard red white and blue!
Oh yeah I have seen this one. Optical illusions are crazy. Thanks for sharing your experience from school! I would have loved to have this topic in school
:)