The Best Hair Colour For?

I like trippyhippyhelena's answer, but your heroine will stop dyeing it as she evolves after realizing that her red hair does not define or mark her as an impetuous, fiery person, which is why she always hid it-- she thought she was being stereotyped. She realizes that she really did have a fiery temper, hair or no.(vote for trippyhippyhelena if you like these ideas BTW.)