Funny ... I looked into powder coating them and was recommended not to as it chips easy end up experimenting with my spare wheel ... after using a etch primer I painted just the spoke area with aerosol duco paint can and just left the flat flange area bare ... end result much easier to keep looking good as the flat flanges are easy to polish the rest just get a wash I painted it a dark gunmetal gray but will be changing that to a nice dark metallic red
doing the whole rim might be a bit to much (no matter what colour you use) as I said I left the flat sections (which are easy to get to for polishing) and have no regrets
Maybe go two-tone. Red around the rim but some other color on the spokes and center. Any halfway decent powdercoater could do that. Red and chrome (ie very bright silver)? Depending on the color of the bike. Or red and a black center. Just a thought.