What color contacts should I get and how can I persuade my parents?!

I have mid brown hair tan skin and darkish brown eyes. I would like a vibrant purple since I'm a scene kid ;) but I really want the Picasso purple three blend colored contacts. It's so vibrant and beautiful. I have biggish eyes. I just don't feel like I was supposed to have brown eyes it just doesn't fit me. But my mom doesn't agree. My dad doesnt care but my mom thinks it's dangerous. I'm 13. I'm responsible enough to clean them and take them out. How can I show them I'm growing up? We've already went over this but she still doesn't listen. How can I convince her to grant me freedom of me paying for my own contacts?