White's Illusion

Oor

The rectangle on the left is mostly surrounded by white. The rectangle on the right is mostly surrounded by black. Which rectangle appears lighter? Use the slider bar to move the rectangles back and forth. As the rectangles overlap you see that they are identical. Colors appear lighter when they are surrounded by white, and darker when they are surrounded by black. This is a color comparison problem using two identical rectangles against a b&w background.