to make it look/flow well. I think the color is a moot point though; darker colors will just more effectively hide the imperfections I referred to above. If you have a good looking piece, the color shouldn't really matter. IE: Twin Z rear diffuser looks absolutely spot-on on every Z I've seen; even on colors I don't like. In fact, one of my favorite of Z colors (Diamond Black Pearl) doesn't show the Twin Z rear diffuser as well as a more contrasting color to the matte black diffuser material. Whereas a Bomex Supra-type spoiler just looks awful no matter what the color.