What's Going On?
The "Bird in the Cage" exhibit relies on the ability of the brain to interpret negative afterimages as complementary colors. The relationship between primary and secondary colors, and their complementary colors, is illustrated in the color wheel.
A mixture of any two primary colors of red, yellow and blue will produce a secondary color-orange, green or violet. For example, when yellow and blue are combined, the resulting color is green which in turn is the complement of red. Red and green are therefore complements of each other. Thus a mixture of any two primary colors produces the complement of the remaining primary. Complements have the power to either neutralize or enhance each other, depending on how they are used.