In the above picture both the A and the B squares are actually the same color. But because of the way they are drawn, they appear to be different colors. Don’t believe they are the same color? Click this link to see a “proof” image.
The illusion is based on a study by Edward H. Adelson, a Professor of Vision Science at MIT. The study is of light perception and the human visual system. Our eyes actually see the correct colors, but our brains reinterpret them based on the surroundings.
I found the entire study fascinating, though his paper was pretty technical. Still worth reading even if like me you don’t understand all of it. So check out his paper here: Lightness Perception and Lightness Illusions
And if you want a more simplified explanation of the above picture read this: Why does the illusion work?
