I am 19 years old.. and I am still fighting my mother about getting a mohawk. How do I handle this?

Ok, so I am a 19 year old guy and I still live at home (due to our messed up financial situation, I don't have a job right now, but will to get out). I have to live here right now. Well, me and my mom always get along but she is a tad more conservative than I am. I tend to dress a tad more extravagant than some, not out of any yearning to be different, but just because that's how I like to present myself and what I'm into. Everyone has their own tastes. Well, since I was 13 her and I have had a constant dispute about me wanting a mohawk...and her completely rejecting the idea and saying no. Well, I respect my mother enough to say "alright..." . I am in college, and I will soon be getting out soon to go into the graphic design field (a field where you don't have to look very conservative.. actually with a lot of jobs it doesn't matter at all how you look... especially if you're a freelancer) and it won't really hold me back from getting a job. She has a problem with listening to my side of things, when I ask her she just says no, and that's it. How do I get her to see I'm an adult (don't say get a job because I want one.. but our financial situation right now doesn't allow it), and how do I get her to see it's just a haircut. I have never done drugs, been drunk, gotten in any real trouble and I'm one of the most polite people you'll ever meet. She has no reason to be saying no to this. And I respect her! Something a lot of kids don't do nowadays to their parents. So yeah, any help would be fantastic!