Publisher Summary This chapter discusses color appearance, which refers to the aspect of visual experience that goes beyond perceived intensity. Color appearance is a mental phenomenon, not a physical one. No wavelength of light is endowed with a color. The technical definition of color vision is based on discrimination rather than appearance—color vision is the ability to distinguish two lights regardless of their radiances. In general, the color appearance of an object is not related in a simple way to the properties of the object alone. Perceived color can depend on the source of light illuminating the object, the spectrally selective reflectance of that light by the object, other objects in view, and the current state of the neural pathways of eye and brain that mediate visual experience. Of these, only the spectral reflectance is a property of the object.