I picked up some Krylon Fusion today in "satin white". I cleaned up an old junk tire I had laying around (knew I'd find a use for it! lol) with some tar and grease remover and a scotch-brite pad. I let it dry, then went to town with the Krylon.
It actually turned out a lot better than I had anticipated. The "white" was really close to the color of a true white wall. It seems to stick to the tire pretty well, but it does scrape off with a forceful finger-nail. I'd say, for the cost, it's worth it for sure. I think I'm going to go this route at first, since I have a few hundred miles left on my current tires, then if it works out and holds up, I will do the same to my new rubber.
I can get pictures if anyone wants them, but be warned that I didn't tape a "stripe" or anything on the sidewall, just sprayed and let it dry. Let me know.