Go for a solid colour, one of your "good" colours. Twice I've taken ID photos in colours I didn't realize were really not good on me until after seeing the pictures (a coral/white breton in one, and a cobalt top in another). The results were bad enough I got rid of the tops posthaste, but had to live with the photos for years. My best ID photos have been in a charcoal sweater, a black watch plaid shirt, and a chambray shirt. Neutrals for the win!
Also -- nothing too low cut or you risk looking topless in the final crop (happened to a friend who was wearing some kind of spaghetti strap tank for hers!).
