You can remove anodizing, but it also takes a layer of aluminum with it, as the colour is built into the surface oxidation layer. I've done this a few times over the years. For parts with crucial tolerances, it's bad! Screwed up set of 1.5* rear uprights this way.
I've heard of getting parts "re-anodized" but haven't seen the process. Not sure if it's simply a matter of repeating the process in a different way, or something more involved.