Sand it back smooth first then spray with semi gloss black spray paint. Use about three coats. Did that with my stereo surround and it looks stock now.
Very very tidy car mate reminds me of my old ute. i did all the usuals and CPR6 manifold spacers diff gears etc etc. ended up making like 550-650nm torque and cant remember the HP. used to do 3rd gear line locks haha