Really it depends on the girl. Here skin color has to match the hair or else it simply looks odd. Personally I think dirty blond but not light blond is extremely attractive... but on the other hand I can't think of anyone I have met whose hair I think is more beautiful then my current girlfriend's and hers is darker brown. She can put the hair in any style and still have it look either beautiful, cute, or sexy. But take into account I am extremely bias in this issue.
I like black the most, brunettes are hot too I think. I don't like blondes or redheads for some reason a lot of guys seem to be into blonds though; but, if this is a question then you should choose whatever hair color that YOU like best :D If the guy doesn't like you for the hair color you like the most or wants you to be (or look like) someone you're not, then screw him.
As a straight stylist I tend to lean more towards brunette . if your complection matches your hair color that's all that matters . If you think you look good your probably on the right track . Guys just love women in general .