The battery tray and brackets where mounted to the body before it was painted so it should be should the color of the car. However I have seen original cars with a black battery tray. I were told from workers back in the 60ies that sometimes when there were a short supply of battery trays they painted the car without the battery tray. Reason was that they didn't want to stop the assembly line for lack of battery tray so they added the battery trays after the body were painted. I have seen this on two unmolested factory cars so it seems to be correct.