system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 - How are color assignments made for remastered movies that were originally in black and white?

Is it by choice or is there are way to decipher color based on the tone of black and white?
gpt
Sometimes there are surviving costumes or props or even sets that you can refer to to see what the original color was. Sometimes there are some color photos from the set, even though the film ended up in B&W. And sometimes it's an educated guess based partly on how dark or light an area appears in the B&W film, partly on what colors were fashionable at the time, etc.  


And sometimes they really just have to guess. And for things like skin tones, or settings, it's easy to figure out. Like if part of the film happens in a desert, you can pretty much guess what color the sand dunes would have been, or if it's a scene filled with working-class people walking home from work (as an example) we know that the average worker wouldn't be wearing fancy clothes to go work in a shipyard or a butcher shop, so we'd assume that their clothes are very basic colors.  


There are also loads of historical documents we can refer to, which can take a lot of time, but you can find really great info about clothing, building materials, popular paint colors, all kinds of good stuff.