Well you said doctors. There are two doctors I know at my local clinics / hospitals that have very unnatural color in their hair. I've known many engineers with visible tattoos, piercings, and/or wild hair colors. Basically every nurse at the hospital here has bright colored streaks. It's more to do with the workplace policies at this point. And as more young blood fills those work places and evaluates policy, the hiring discrimination based on hair color goes down.