Primer colors under armor?

Modern American armor is generally primed in that base (flat) forest green that is the base coat for our NATO 3-color scheme. When I visited the UDI factory in York, PA (where they make Bradleys, MLRS, AAV7A1s, M88A2s), they dunk the aluminum armor components into a chromate solution and they come out a greenish yellow color.

A lot of the vehicles being built are now being produced in desert tan, but parts are still being supplied in forest green (like road wheels, a fender or storage box cover). So the vehicles are starting to have a base coat of tan. If the vehicle is going to a unit that needs it NATO camouflaged, it gets the scheme applied. Otherwise, they just paint the tan vehicle with green parts with a desert tan overcoat.

German armored varied though-out the war. Most were red-brown primer, most later on in the war left the factory in primer, and left the rest to crews.

japanese had a simular color to red-brown primer, that would work fine

British WWII armor was mostly a green primer, same with American WWII armor.

The M-60 series was primed with a red oxide primer, I think the M-1 family is too, but I'm not positive about that.