I know some of their older GBs had the bare metal GB shells, but as far as I know ALL their guns coming off the line right now have black shells. I know I could be wrong, but now that they've started releasing replacement GBs, all of them pictured including the Scar GB was black.
When I get mine I'll be installing helical gears, AB mosfet, Guarder 110 spring(I like the consistent FPS it gives), G&P 120 motor, SCS nub(if possible) and a systema bucking. It may all not be needed, but it's all just for personal preference based off past experiences with the parts.