If you had something like this powder coated how could you do more than one color?
Hot, humid air is less dense than cooler, drier air. This can allow a golf ball to fly through the air with greater ease, as there won't be as much resistance on the ball.
This is a good question of how the asian sport car rims are done.
Basically you'd put a barrier over the part you don't want powder coated.. a grease type material.. follow normal procedures.. then wash it off.. 2nd color then..
OR you could do it all in one pass and then "Polish" off the areas.
A good place can double bake this..
Since it is aluminum, paint may be an easier answere.