Highlights for dark brown hair?
A light brown, or dark blonde would look good. If you get it done by a proffesional, they'll have the sample colors that you can put up by your hair to see what looks best.
caramel or like a peanut butter type of creamy light brown would look best!
I loved the way it looked on mine!
go for low lights rather than high lights, it lloks fantastic and really natural, ask your hairstylist