Does anyone know what the factory prime coat color used to be on Shermans? Stevem
Standard primer gray.
Are you asking because you want to… show some paint chips or scrapes? Consensus is that US equipment was extremely well painted and near never chipped. The more challenging (and realistic) effect with US olive drab is to weather the dust pattern correctly. Look here:
http://www.ww2incolor.com/gallery/albums/us_army/sherman_in_italy.jpg