My first would be brunette. Kind of a darker brunette though, the darker the better. Second would be dirty blond, third black. I am impartial to redheads, but for the love of god do not dye your hair white, fire red, purple, or any other color that could make me mistake your head for a skittle.
Least favorite- some unnatural color, like bright red
Why? Because everyone these days is trying to be someone that they aren't. It's like people are afraid to let their true selves show. I can appreciate any natural hair color on a woman, but only if SHE appreciates it herself.
I prefer any hair color on the opposite gender.It doesn't really matter simply because it is by far the last thing I am thinking about when I see someone I am attracted to.I am usually thinking about their face,body and personality if I am able to get a glimpse of it.Definitely not thinking about hair color.