The color that I used on the 46 engine is the Krylon Fusion from a rattle can. It's made just for plastic and sprays very nicely and I have not had any orange peeling with it yet. I still put it on top of primer as that seems to give it the dark shine to it and the top it off with some Future.
Here's where you can get more info on it.
http://www.krylon.com/main/product_template.cfm?levelid=5&sub_levelid=10&productid=1751&content=product_details