Pick up some Krylon "Fusion" paint to match your upholstery color. Fusion is designed for plastics and works very well.
The key is to make sure the plastic is clean. The best way to clean it is to wash it in VERY hot water with TSP mixed into it. TriSodiumPhosphate is a degreaser and is available at any hardware store. Use as hot a mixture as you can stand and scrub the parts with a scotchbrite pad. This will give you good tooth for the paint and make sure any Armorall or silicone is removed.
Keep the parts clean and grease free and you should have no problems with the Fusion paint.
Mark