Chickens DO SEE RED LIGHT.
Birds in general have very good color vision, chickens are no exception. For one thing, that is why they go after blood so much and start pecking -- they recognize the red color quite readily.
Red light decreases picking/cannibalism (somewhat anyhow) for two reasons: first, a red bulb puts out a dimmer light than a white bulb of the same wattage, thus the overall effect is dimmer and apparently this is more calming (or less overstimulating) to them; also, in red light, EVERYthing looks red, blood looks black (as do black things of course), so there are no obvious targets to attract pecking.
Pat