Why are all the long haired princesses Blond!?

Seriously.....Aurora, Rapunzel, Buttercup, Amalthea.... Ariel and Thumbelina have red hair not brown. Snow White and Belle have dark hair, but theirs is short. I can't ever do movie costumes right without bleaching my hair or cutting it, or so it would seem. Granted, Cinderella has short hair and she's blond, but still, why aren't there any LONG haired brunett Princesses?