This illusion is of a desert on the bottom that is exactly the same only flipped over. The top is divided between the colors green and red.The center dot between the green and red is looked at for about 30 seconds without looking at anything else. Then when one looks at the center dot on the bottom with the desert, it does not look the same anymore. Beau explains how our brain was trained to see the left side as still under the color green light and the right side as still under the color red light. He describes it as our "new normal".
Beau explains how the two squares in the center of both rectangles are actually the same color. We see the two squares a different color, not only because of the surrounding rectangle colors, but also because of our learned behavior in the past. We associate objects in dark surroundings to be in shadow, causing the square in the darker rectangle to look lighter. It's the law of physics.
Beau made this optical illusion himself a few years back. The top brown square on top of the cube is actually the same color as the orange square on the side of the cube. This optical illusion is better explained in the Ted Talk video by Beau. I found all these illusions very interesting.