At the factory, the wheels...less tires...hung from hooks. As the wheels went into the spray booth, a painter applied the color coat to the primed wheel but only to the side that faced out. The back of the wheel did not get painted except for some over spray.
Lug nuts and the front wheel grease covers should remain natural color. By the way, drums should be painted a semi gloss black, although everyone today applies a longer wearing gloss black. In fact, all suspension components, including the frame and shocks should be painted the same black.
There is a specific assembly process that the factory used. I can detail if anyone's interested. I learned this at a KF retirees banquet I attended several years ago with Ken Mericle, a KF retiree himself. I sat at a table with a group of gents whose job it was to attach the bits and pieces on to the frame. I learned alot that day!