Most color-based systems are sensitive to changes in a viewing environment. Although human skin colors fall into a cluster in the chromatic color space, skin-color models of different persons differ from each other in mean and/or variance. Even under the same lighting conditions, background colors, such as colored cloths may influence skin-color appearance. Furthermore, if a person is moving, the apparent skin colors change as the person’s position relative to camera or light changes. Therefore, the ability of handling lighting changes is the key to success for a color model.