I’m just starting senior year, and over the summer I put some purple streaks into my naturally light brown hair. My mom was worried that it may affect my chances of being accepted into a BFA program. I’m hoping it doesn’t matter as long as I look like my headshot when I audition! But I’d like to hear opinions-should I dye over the “unnatural” streaks before auditioning or does it not matter?
Part of me wants to say be who you are and show them who you are. On the other hand, part of me feels that the look of purple streaks may limit you in certain programs or pigeon hole you (“edgy” for example) in a certain way in the eyes of particular auditors and that it may be less risky or less limiting to keep your hair in a more natural color and play around with it again after auditions. Another valid view is if a program isn’t interested in such a type or look, maybe you would not feel right in that program anyway.
Keep in mind that for many musicals when it comes to casting, you won’t be able to play a role with purple streaks either.
You can have it both ways. Put your mom at ease and dye it back but buy some purple extensions that clip in which you can later decide to leave in or take out for the audition depending on how you want to present your self to a particular program. They will actually hold the color as opposed to a fantasy color dye on natural hair which fades so quickly and is a pain to maintain. Win win.
My daughter (who is only a high school sophomore) has brown hair with blue streaks in it, so she’s very interested to hear everyone’s opinion on this for BFA auditions! Right now, for regular auditions, we use brown “cover-up” hair spray. They have it at drugstores like Rite Aid and Walgreens in the hair dye section. The cover-up spray is really meant for women who dye their hair because they’re going gray - they use the spray to touch up their roots between dye jobs - but it works PERFECTLY for covering blue or purple streaks in your hair when you want to go on an audition. 
And the spray washes out when you wash your hair.
So if you decide to play it safe and have brown hair for college auditions, but you don’t want to get rid of the streaks in your personal life, you could use that brown cover-up spray.
D has a friend from a couple years ago with a very edgy vibe- including short black hair with bright blue streaks in front. She deliberately chose to audition for programs she thought would “support” that look. I don’t have specifics of her BFA journey (I didn’t know her well) but I know she ended up at Pace. Recently D showed me a picture of her In summer production of Mary Poppins. (No idea where, wasn’t paying attention) but the caption was “a good wig can work wonders”. Didn’t seem to have stopped her from getting into school, or getting cast. Perhaps it even made her memorable.
With that said- I would tend to err on the side of caution- and like both halflokum’s and actor parent’s suggestions for how to give yourself more versatility in casting