I'd go with toe's assessment, and add that you can go to websites like powderbuythepound and Rosie's and buy the color you want. They all shoot the same (although they might cure differently), so presenting a half-pound of your favorite shade of red to the powdercoating shop shouldn't bother them. You can get RAL colors, which are a spectrum of industry standard shades, or the specialty powders unique to the various websites. If a clear coat is recommended, they come in many lusters from flat to 100% gloss. You might want to choose your clear coat based on the shine you want. For example, to preserve the look of blasted aluminum, you'd want a zero gloss clear. To make a candy colors pop you'd want high gloss. The powder seller's websites are usually really good at explaining the differences, and I've never been disappointed by the phone conversations I've had with any of the suppliers I've dealt with.
A caveat on powder coating used parts: They must be cleaned to the pore level to remove any oil or other contamination. At the 400ºf cure temp anything in the metal itself will outgas and ruin the powder. Get the job done sooner than later to minimize the metal contamination and let the shop do the prep. You'll still beat the cost of oem red covers.
