I painted mine and they look good. I scuffed 'em up pretty good, primer coat, then the spray paint. I used Krylon metal paint for the rims and Krylon Fusion for the plastic center caps.
However there are a couple of spots where the paint has come off.
In hindsight I probably should have sprayed them with truck bed liner. That stuff's hard to come off. Eventually I'm just gonna go buy some black rims.
I just stuck masking tape on the tires and sprayed away.