Well that's tough....
I've been reading through my AMT manuals...and didn't see a specific color set you are supposed to paint...although the Revel kit i have gave the colors used to match the one on the cover...
Usually GM engines are painted Orange (alot of them get painted redish/orange), but most of the boys that like the blue oval's that I know of paint their blocks blue...
Now this is real life...I'm not sure what color, if any, they came from the factory.
I'm very new to this hobby, but I would imagine that you would paint different parts of the under carriage different colors. I see the frame as black, exhaust as a metallic color, oil pan blue or chrome...
Stuff like that...
Then again...I'm not 100% on what you are trying to accomplish...
Anywho...that's my two cents...