While it's not exactly a deal breaker, I'd have to say I always find a woman becomes more attractive to me as a brunette, while if she gets a dye job I find it a bit less attractive (not to say it's the dye job, itself, that it unattractive... if a natural blonde dyed her hair brunette, I'd find her more attractive). Red heads fall between the two in terms of attractiveness to me.
A (One) ...
Brunettes.