There is vinyl dye that comes in spray cans if I remember correctly. I had a friend do it to his seats in a '81 camaro or whatever it was. Came out okay.
Pics of my intrerior.
I think that a light sanding of the parts also will help the paint stick better. I also clear coat my parts. This makes the color which sits in the sun alot, last longer, as well as matches the exterior perfect.
I painted the interior of my '02 GTs plastic pieces and during the summer the paint started bubbling up and coming off! Stay away from Dupli-Color interior car paint.
been looking into this myself. black also. I have come up with the Parisol vinyl dye as an option, but i havent used it yet. It's a bit pricey, but im told its the best.