How to convince my mom to let me dye my hair?

I have very pale skin, and plain brown hair. I feel like spicing things up for school next year, and I want to dye it a dark red to match my personality! I've been called fiery and a spitfire, but very funny and sweet. I tell it like it is, but I'm not a b*tch! Haha :) My mom doesn't want me dyeing my hair again (I temporarily died it a caramel color last year, it was really pretty) but half of my hair is the caramel color from last year and the top is BROWN. It looks funky. How do I get her to let me go get my hair dyed? I'll even buy a dye off the shelves at WALMART! Thanks :D Yall are the bestt!