Rust Oleum in rattle cans. White. Use colors for marking if you like to color code stuff, I do. That oil based paint adheres better and lasts longer than the cheap water based stuff. Unncessary to paint the inside, That mil spec stuff from the factory is difficult to improve upon. Powder (not power) coating is definitely the best, but spendy. I saw some 50 cal cans recently for something like 30 bucks each. I pay maybe 6 or 8 bucks in Olive Drab.
Don't Wanna Die Askin' for Another Chance