Well, normally with powdercoating there is a set color that you can choose from. I'm not sure if they have anything that is as white as Alpine White, but I'm sure they might have something really close. I've had my wheels powdercoated at this shop before and they do a really great job. The only problem is that you have to send them in.
In your case I think painting them would be more ideal, but it won't be as durable as powdercoating.
If you're on NorCal, this is the best place to take it to.
http://www.wheeltechniques.com/index.html
Poweder Coating info below.
Crosslink Powder Coating
2310 Patterson Industrial Dr, Pflugerville, TX 78660
Phone: (512) 670-0334