Originally Posted by HarryT
It's certainly true that red-green colour blindness (by far the most common type) is far more common amongst men than women, affecting around 8% of men and only about 0.5% of women. The reason for this is that it's carried by the X-chromosome, of which men have only 1, but women 2, and a woman will only suffer from the condition if both her X-chromosomes have the genetic defect.
The first person that I ever met, with color blindness, was a female classmate. It was during our health class, when she found out that she was color blind. We thought she was joking around, when she said, she "couldn't see it." Then the teacher showed a test that only she could see, and the rest of us, couldn't see it.