Women being pushed into boxes with labels stamped on 'em.
Asking what size boobs / hair colour is the best is the same as asking what are the best wheels / paint colour for a vehicle. Without seeing the frame of the vehicle and how it presents itself you will never make all models look good with just one choice of size & colour.
It all depends on how the girl carries herself...and whether her hair colour suits HER look and whether her breasts fit her frame. Don't get me wrong, I love boobs...but boobs on their own are pointless.
However, no matter how hot she thinks she is, if she doesn't have sex appeal AND something other than her looks that attract me, then I couldn't be less interested. Keep in mind, sex appeal is not about what you look like.