English: Illustration of colour metamerism by CMG Lee. In column 1, a ball is illuminated by monochromatic light. Multiplying the spectrum by the cones' spectral sensitivity curves gives the response for each cone type. In column 2, metamerism is used to simulate the scene with blue, green and red LEDs, giving a similar response. Curves are from http://commons.wikimedia.org/wiki/File:Cones_SMJ2_E.svg .