Great, thanks for the advice! I think that's cool about your bank advisor--I'm not sure why tattoos and dyed hair and piercings (if it's done well) must be separate from business casual, anyway .
Sayjo, I agree, it's hard to know if unnatural hair color would be acceptable at the hospitals and clinics I'll be working in (unlikely). I think I will take your advice and dye it for the first semester and play it by ear from there. Hopefully by then I'll be bored of it and won't miss it if I do end up having to dye it back.