Found a film on You Tube which is quite something if you haven' t seen it. It is a 1941 Army film telling about the US Army tank corps to encourage people to enlist. It is in color, and there is footage of M2 medium tanks,the ancestors of the Lee and Grant, as well as M3 scout cars and 75mm pack howitzer. It is done with some humour with George Tobias, a famous character actor at the time. Here is the link
http://www.youtube.com/watch?v=MN6htrp8Pnc