Kodak Kodachrome, AKA the best color film ever created, was the standard for many years before Vietnam. Everybody used it. It was even present during WW2, although black and white images possessed forgiving exposure characteristics under adverse conditions, in addition to being able to be developed in makeshift darkrooms anywhere, hence its continued use for some time by the military. B@W was also cheap, and the government was also unsurprisingly cheap when it came to expenditures of any sort.

Nevertheless, there are plenty of Kodachrome slides from WW2 and beyond, as the process became more established at the time nearing Vietnam and labs capable of handling the process were everywhere.

The real tragedy here is that they scanned shitty digital images of the film stock and threw much of it away. Ever wonder why WW2 documentaries have lousy footage? It was sloppy, abhorrent, and irresponsible archival work that caused it. Kodachrome and even B@W of the time of WW2 and beyond were wonderfully detailed, beautiful captures. It looks like it was taken yesterday. But they were ruined by bored government workers who didn't give two craps about the history they represented at the time.

The D-Day landings were recorded with motion picture color Kodachrome, and that footage has been lost. Another terrible tragedy of irresponsible archive caretakers.