It merely means I may find a certain hair color more appealing on a man in general, but it doesn't mean I'll date that guy. At the end of the day, if he's smart, sweet, and good looking, it probably doesn't matter what hair color he has.
And to be honest, for me, it's not a hair color preference. It's the COMBINATION of hair color and eyes: dark hair, and bright blue eyes (good example would be Ian Somerhalder).
So if the guy I'm interested in happens to HAVE that combination, it's like the icing on the cake. Day-um.