statistically, the same way that people have on average slightly less than one testicle.
the genes for the cone cells in your eyes are on the X chromosome, so women have two shots at getting them right. men have one, so men are more frequently deficient in color vision. reportedly there are also female tetrachromats, who have a bad
and
a good red cone cell gene and produce both, and so can discern colors even better.
personally, i'm male, but have
perfect
color vision.
the other factor is naming conventions, which are cultural. women are taught to focus more on many color names (makeup, fashion, etc, are all targeted at women). this isn't so much discernment, but how we choose to name things. we had a guest lecturer in our seminar class in college once talk about this, and rehashed this same tired point. she showed a color, and said she's call on a male student and a female student. she called on me, and i told her it was lavender. "bad example," she says, and calls on my female friend who is sitting across the room that day. my friend said "purple."
i was an art major. she was a bio major.