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Colour Input by Humans

The human eye can perceive a very wide range of colors compared with gray scales. It actually has different sensors for colour than for monochrome. Colour is detected by ``cones'' cells in the retina that distinguish a range of different signals, while black and white (mono-chrome) is dealt with by rods. Rods are actually sensitive to much lower light levels (intensity/power), and are particularly good at handling motion. Cones are specialized to higher light levels (hence why colour vision doesn't work in dim light levels such as during dawn/dusk/twilight).