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

So i'm 12 years old and my hair is naturally light brown and my mom let me get blonde highlights which I'm growing out bc I dont want them anymore. I want to get my hair dip dyed dark blue. my mom was a little unsure at first, but she liked the way my highlights turned out, but I dont know how to convince her to let me get blue. what should I do bc I reallyyyyy want this??