Remington uses several finishes.
There is the polished blue, standard blue, sand-blasted blue (express), camo (painted over Parkerizing I assume), Parkerizing (on their police guns) and finally their electroless nickel marinecoat. Parkerizing will always have a grey hue to it. It's perhaps the best finish available for applying a finish over.
One of the steps in parkerizing is to soak the gun in some sort of oil to fill the pores. If you plan on painting the gun afterwards, SKIP THIS STEP. For the best adhesion, you want to take the gun out of the rinse tank, let it dry, and then paint it. This will allow the paint to soak into the crystaline structure of the parkerizing and it will stick much better.