Incredible Color Constancy Illusion

"Here's an amazing effect called color constancy. This illusion is caused by the separate red and green illumination of the 2 cubes and by the apparent shadows that are cast on their front surfaces. We interpret colors as being constantly the same even if there are shadows or different illumination conditions (such as the red and green "lighting" effect). We also define/perceive colors based on their surroundings. The end result is that we see the marked square on the left cube as being light blue (cyan) and the marked square on the right cube as being red. Removing their cue-producing surroundings and placing them next to each other reveals that they are both, in fact, reddish-grey".