That OPFOR, tho
This just in from the U.S. Army Quartermaster Museum:
This C.1948 shirt was used at Fort Riley, Kansas, the site where the Army’s full-time Aggressor Force training concept was articulated from its inception in 1946 until its discontinuation in 1978, at which point transformed to the dedicated OPFOR groups at Forts Polk and Irwin.
Your standard OD had been dyed darker and collars and shoulder straps sewn over in red to mimic Warsaw Pact style uniforms.
Full video below: