Paint manufacturers produced green paint for the army in great quantity, their surplus sold off to lathe manufacturers. In the years after the war, machine shops continued to buy green lathes if they had machines in that color, touching up old equipment in green. read more
Some few builders did make green their standard color, but gray seems to have been the prevailent color. A shop owner might have a preference for some other color, and any machine tool builder wanting to make a sale would offer to paint a machine tool any color the customer wanted- unlike Henry Ford and the Model T cars. read more