When we think of America during the Great Depression, we often picture it in shades of grey. It was a grim era and nearly all of the photographs we see are in black and white.
When I was at school we used to have a lot of old National Geographic magazines, going back to the 1920s. I think they were from an old collection donated by one of the parents. They had lots of colour photos from all over the world, but in those days relatively few were Kodachromes.
Kodachrome (which I believe has just ceased production after more than 70 years) was a subtractive process film, and in developing (which could only be done by Kodak) the metallic silver was replaced by colour dyes. This made it practical for small format cameras (called miniature cameras in those days), like 35 mm.
Most of the pictures in the old magazines seemed to be taken on Dufaycolor, which was an additive process film (and thus more like digital cameras today). It had red, green and blue dyes pre-printed on the film base in a pattern of blue and green squares and red lines, with the silver emulsion put on after that. The film went in the camera backwards, with the emulsiion facing away from the lens, and when developed, the silver went according to the red, green and blue filters it was exposed to. So when projected, the colour was reproduced. It worked fine on large format film, but on small format the pattern of lines and dots was noticable, and subtractive films like Kodachrome won in the miniature camera market.
But I saw Dufaycolor film advertised in a photographic magazine, and ordered some from England when I was still at school to try it out. The colour seemed much more accurate, but it only let through a third of the light of subtractive films, so when projected the slides looked rather dim. But for reproduction in magazines like the National Geographic it worked fine.
Earlier colour photos for reproduction in magazines were made by three-colour separation
s negatives, and their colour is far more accurate today than the faded dyes of subtractive film like Kodachrome. For more on this see here, with some fascinating photos from an even earlier period -- Russia before the First World War.