that works because your eye actually gets "tired" of seeing one color and sees its opposite when you look away or some ****.

I remember doing some kind of wierd test in grade school at the science museum. You would stare at this BRIGHT GREEN paper bird on the wall for as long as you could and then quicklyl look over at a cage. there was a red bird there for a few seconds until your eye fixed itself.

Try staring at something intense/bright (not like a headlight bright, but a bright color (like your girlfriends hot pink thong) then look away. You'll see a hot green thong for a while.