[Nyororin]

....

Are you Japanese?
No?

Then it doesn`t matter.

Seriously, the only time hair color really matters is if you are Japanese and bleaching your hair. You`re not Japanese, so no one would expect you to have black hair. In fact, it seems like blondes get MORE opportunities in Japan because being blonde is more "typically foreign", so is a sort of favored trait in businesses wanting to have a foreign face.