Sun-In, roots, and removing them (HELP!)

My mother has always been slightly obsessed with blonde hair so, when she saw bottles of Sun-In spray on sale for $1.99 at Big Lot's, she bought me two of them. This spray is a product that, sprayed on hair and taken in the sun, lightens hair. My hair has always lightened in the sun, but now it turned a "nice" (to her) blonde shade, though it was a bit orange at the beginning. It faded to a cute blonde shade, and I-who had never even had highlights, much less dyed my hair-received a lot of compliments on the beachy look. Well, it's two months later, and I have almost an inch of roots of my natural dirty-blonde (or light brown, whatever) color. This is not attractive. I want to know how I can just get my old, natural color back without damaging my hair, possibly at home. Please help me out, I'm pretty tired of staring at my ugly head in the mirror every day. Thanks a bunch.

Edited by cheri488