[doc30]

Getting back to the topic of the thread, I find the topic of color vision rather interesting. I have a number of color blind members of my family, including a nephew with total color blindness -- no color receptors at all.

Even though this article doesn't mention it, it seems red-green color blindness would be very similar, if not identical to the dichromatic vision of other mammals. So your family members may have color perception similar to a dog or cat.

[js1138]

Possibly, but there are a number of different variations on color vision among humans. The most common one may be as you describe. The interesting thng is that color deficiency varies with luminosity. Color blind people can often distinguish colors better in bright light.