Anodizing is a conversion process to aluminum. It converts the surface of the aluminum to a specific type of aluminum oxide. If you paint it, the anodizing can't get under the paint to convert the surface. You would not want that.
For those that don't re-anodize, the aluminum will re-oxidize after a period of time in air, but it's different than the oxide structure in anodizing. Anodizing is probably more durable for a street car, but for our classic cars that don't get driven 12 months a year, get washed regular, get waxed, etc, regular oxide is probably fine.
If you want those parts dyed a certain color, the anodizer can do it. This is a small spectrum of the colors available.
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