They aren't anodized with a good dye if they are anodized or the paint was bad quality. Good powder coat doesn't have those problems.
Silver painted alloy rims on my '86 Volvo came off a '85 vintage 750 (12 spoke design) and they make the car look good. After 26 years in the sun of California and past 5 years in AZ they have faded, usually evenly unless chemically contaminated, and faded out to white-silver; it was good quality paint and they need refinishing but it takes decades to make them do that. Now to find 30 year old quality paint today...