There are paints out there just made for plastic/composite parts that you can use. You can usually find it at most auto parts stores. If you can't find it see if you can find an automotive paint supplier that's open to the public in your area since they'll have what you're looking for.
As for the paint that I used, I used the Dupli-color 3 step anadized paints you can get at places like Advance Auto, Auto Zone, Wal-Mart, etc. You can get it in several colors - purple, blue (which I've got on my 99 pics in my 1999 gallery), green, gold and red. Those consist of a adhesive coat, a base (anadizing) coat and the actual color coat. To do everything that I've done in/on my car (interior pieces - trim pieces, window pieces, speaker covers, t-top holders, etc and under my hood - air filter box, strut tower brace, TB cover, fuse box cover, etc) I used 3 cans of adhesive, 5 cans of base coat and 8 cans of color.
A couple of hints if you do end up painting yours - 1) make sure you do it on a day that you've got the time since it isn't something to be rushed and with the paints that I used you have a time limit on how long you can let things sit between coats; 2) make sure that you do it on a day when it isn't windy or that you've got someplace to work like in a garage with the door open so that junk/dust/etc isn't flying around to get into the wet paint, 3) make sure that you clean all the parts really well to remove any grease, fingerprints, etc off the parts and to let them all dry completely before you start. If you don't you'll be able to tell where every spot of grease, fingerprint or piece of dust is on the part after you've painted them. 4) make aure that you follow the directions with whatever paint you use to the letter. If not you'll be disappointed with the results.
One more thing, I'm not sure if you'd want to do this or not, but what I done is I got matches of the pieces that I wanted to paint (ie extra speaker covers, trim pieces, etc) where I could (couldn't with the strut tower brace) and I painted those. Some of them were sun faded and things like that so painting them didn't matter but I kept the originals that came on my car unpainted and I've got them stored in a box in my basement. I done that cause then in the future if I wanted to get rid of the painted items for some reason or if I ever wanted to sell the car and needed to take it back to original I could with no problems or having to find unpainted parts that were in good shape or having to buy new parts from somewhere.
But if you need any more info about painting those pieces let me know and I'll help you as much as I can.