If these are the same "concours correct" arms I bought from LM Mustang, they are already finished just as the factory did theirs. That is to say, the uppers are SG black and the lowers are half black and half natural.
As others warned - install 90-degree grease fittings on the upper arms and grease every fitting as soon as you've mounted them on the car.
BTW - These arms are actually the Canadian Mustang (aka American Pony) arms and bushings (Midolyne). Pretty good stuff - I think you'll like them.