You could try to search for it, I know there was a post about some members painting it black. Im considering it too, I think they used Black grill spray paint to do it (do to the heat). It you do it, get us some pics.
I just used hi-temp spray paint. Didn't bother to prep other than rinsing the loose stuff off. Used a scrap piece of cardboard to prevent overspray.
Did not paint the heat shield nor the top of the muffler. I also painted the tip.
if you look around this forum,you'll find an answer and even photos of my muffler which I have sprayed with black heat resistant paint available at most car parts dealerships,I've bought mine at Canadian Tire,it will not only protect and extend longevity of your muffler but it looks cool