I am red-green color blind. That is, I fail those tests they give you with the numbers concealed in fields of differently-colored spots. But I have no trouble seeing red and green.
I think a better name for my condition would be "color insensitivity." I can see bold blocks of red and green just fine, and I have no trouble recognizing red lights. I have trouble with murky shades, and I would never employ myself as a color consultant, but generally I get along fine. My one practical issue is that I have trouble telling a green light from a white light at night, so it sometimes happens to me that something I took for a street lamp will suddenly turn yellow.
To me the most interesting thing about my color blindness is that it seems to manifest most often, not as being unable to see colors, but as being unaware of them. Once somebody tells me what the number is on one of those test pages, I can see it, and I mean really see it. If I forget what it is, I can't see it any more. I can scan across a green field and not see any of the bright orange surveying flags hiding there, but if one is pointed out to me it leaps into my consciousness. I remember once walking in a field with a friend who observed, "look how red those willows are." I had been unaware until that moment of anything red, and when I looked up at the line of little willow trees by the edge of the pond, they looked at first green. But then some perceptual shift happened, and I saw how red they were.
All of this makes me think that my condition is a glitch in the perceptual software in my brain, not a problem with my eyes. I wonder if other people see as I do, but isn't that one of the great imponderable questions?