How will 10 volume developer with a medium blonde color affect my medium brown with 40% gray hair?

My hair is naturally a medium/dark brown hair with plenty of yucky grays. The only good thing about the grays is that they are evenly dispersed through my hair. I have been getting (expensive) salon highlights for years, but I was wondering: what if I could make the grays highlights? What do you think would happen if I used 10 volume developer with a level 7 or 8 color (a medium or light blonde)? I'm hoping it would have little affect on my hair that is still brown (maybe brighten it?) but would color the grays and make them appear as highlights! What do you think?