Americans like humor that makes fun of groups of people. One category of jokes portrays blondes as dumb. Of course, this is not true. There is no reason that you could not refer to a woman as a blonde, all things being equal. I mean, a person's hair color, especially for women in the west, is quite personal.

Blond for men, blonde for women. Yes, there is a suggestion that the person is stupid, but if you want to avoid this, use "blonde-haired" or the more poetic "flaxen-haired".

There is an idiom "blonde bimbo" that is used to describe women who model themselves on Hollywood stars like Paris Hilton.