What colors do color-blind people see?

I think the answer must be that they see in various shades of white to gray to black, maybe as in an old-fashioned black-and-white movie.

However, there are various degrees of color blindness. I am partly color-blind—or, really, not very sensitive—to red. When I see a traffic light a very long way off I can see a light but I can’t tell whether it is red or green until I get closer.

Actually the color-sensitive cells in the retina of your eye discriminate between colors only in bright light. In very dim light your eye can’t see colors as colors.