Give an explanation of why after looking at red for a long period of time, people then see green when looking at a white stimulus as an afterimage. Image is at start of process.

When viewing a red stimulus, the L cones are more stimulated than the M cones. Consequently, the "red" percept is more activated than the "green" percept, which is subsequently suppressed. People therefore see red. Over time, the L cones habituate and become less sensitive to the stimulus. When a white stimulus is then shown, the green cones respond more strongly than the red cones. Consequently, the "green" percept is more strongly activated than the "red" percept.