To me, looks can spark initial attraction but in order to hold my attention, a girl with great conversation skills and a great outlook will make me see right past her hair color, figure, or whatever other external factor you're concerned about. A true man will understand the struggle women have to put up with in order for them to feel good about themselves. Work on the inside and you won't even notice the color of your hair in the morning.
color doesn't matter as much as weather or not it suits her. I mean she can be as blond or brunette as she wants but doesn't mean she's hot because her hair. and if she was originally a redhead she will look kinda odd as a blond