Exterior & Interior combo ?
It really depends upon what you mean as "best colour combo".
For aesthetics ?
For safety ?
For ease of maintenance ?
I have owned many different colour combos. The one that I went back to, silver with black interior, works best for me. IMO, it best addresses the 3 questions above.
The new F30 (especially the M Sport version) in Glacier silver looks fantastic; it is also a highly visible colour, both day and night and it's easy to maintain
(see photos below).
Alpine white is another good colour, but it requires frequent washing during winter months.
As for interior choices, if you are buying your car, stay away from beige interior. It will not only be labor-intensive to maintain a clean look, it will reduce the resale for your car by several thousands of $$$.
Black and red are by far the two most popular interior choices for the F30.
In the end, there really isn't any one best colour combo, it comes down to what you like. Good luck !
2013-335i M Sport, 8 spd, Glacier silver, adaptive M suspension, variable sport steering, 18" style 400 staggered wheels/tires, M Sport brakes,