Looks appropriate matt black as it is now. Because it's close enough to body color not to attract attention to itself.
Now here's a question: do you consider it a tough functional part of the car or an accent trim which should do it's part to add to the overall aesthetics? If the former, again, it fits just right with the color of the car. If for strictly aesthetics, you might paint it to exactly match.
Another point: since it appears to match the black plastic insert of the center aperture of the bumper/spolier (in non-Tip cars), WTF? Just more reason to leave it like it is.