do you think having halo ring hair at an interview could negatively impact the outcome? as much as i understand it shouldn't, most of the interviewers are ultimately old, white, men
No, it wouldn't. Interviewers see students from all kinds of backgrounds and personalities, and an interviewer who judged based on appearances instead of genuine aptitude wouldn't be an interviewer for very long, I imagine. I also believe all interviews are done with at least two people present, and interviewers are expected to write up a short report on your performance for later record, so they'd need to make up other justifications for rejecting you if appearance was something they judged.
People in all kinds of circumstances and from all kinds of places apply and get interviews. Sure, most interviewers will be older white men (depending on your course, as most of mine were), but in a given day they'll be interviewing both private/state school students, students from different ethnic backgrounds, students with piercings or visible tattoos, or - in your case - students with different hairstyles. It wouldn't be a shocker.
If it's any comfort, I had one of my interviews in a place where part of my music collection (a very 'un-Cambridge' genre, some might say) was clearly visible. Nobody commented or batted an eyelid because it wasn't relevant to the interview.
You should be fine. Best of luck!