Well, I think its all about contrast, inside and out. Dark exterior, light interior and vice versa. I know you talking about exterior shapes, so I will have to go black, when clean, nothing beats it....with a tobacco, tan or red interior.
Black is also the hardest colour to paint a car as it shows every imperfection in the panel work below.
White is nice also, being the opposite end of the scale to black, it also does not reflect so always looks flat, bit like my Grigio Alfieri...and these light colour also dont show the dirt.