Newton: prisms break up (refract) white light into spectral components (rainbow) Even when you send the refracted light through a prism, it cannot be further broken up. Any single component cold not be refracted into a different color (monochromatic colours) When you add colours, it becomes brighter, and may results in life: 2nd prims combining all the colour recreated white light. We perceive the continuum of wavelengths as qualitative different phenomena. Colour is something we perceive efficiently that does not really exist, despite the infinitive ambiguity of this task. Without colour cues, it can be hard to segment things. Green filter: (clown broken down): nose and stars (and some parts of hair_ appear equally bright, but are very different in colour: same luminance throughout image, with one filter, the image"s colours are ambiguous. Only the response of a receptor will tell us something about what light we"re looking at. The output of one cone is ambiguous; there aren"t red/green/blue cones.