They were painted. Get some of that castrol-super clean-cleaner degreaser to clean of the grease and dirt. You can't let it dry on the engine so be ready with the hose. It removes EVERYTHING but the paint so you can tell the original color of the paint when it is nice and clean. Once I was done risning and air drying mine with an air gun it had no residue and was ready to paint.
I don't know what the experts here would recomend for paint but mine came out fine with Dupli.Color Aluminum DE1615 500 degree enamel.
The worst stuff is that 1100 degree paint. It comes off like powder just from touching it.