"Color is the brain's reaction to a specific visual stimulus," says Alan Roberts, formerly of BBC Research (London, UK). "In the human visual system, signals from color-sensitive cells or cones, together with those from cells known as rods, which are sensitive to intensity, are combined in the brain to give several different sensations of color." These sensations have been defined by the Commission Internationale de l'Eclairage (CIE; Vienna, Austria).
