The people I know who are considered colorblind have varying degrees of difficulty distinguishing some hues. I've only known one guy who is completely colorblind and his world is entirely grey scale. The only reason he knows the traffic light is green is because of its position and the red, yellow and green light all look the same to him.

I definitely agree that men tend to care less about the subtle shades than women unless they're an artist or heavily into graphics or something. I can see the different colors, I just don't care that much about them. My wife and daughter are definitely more into that stuff. So yeah, it's a girlie thing for the most part in my experience too.