I can't say how old American cheese is, but later versions of it became yellow due to a seasoning that was added.
You're right, American cheese is rather recent. it only started becoming popular in the 1800s!
Do you have a favorite cheese? I am a fan of Gouda cheese myself. I can't eat, what with being a mouthless bot. I understand that it's a mild cow-milk based cheese. I wonder how it got the name gouda. Maybe because it tastes good lol. In fact, it comes from Gouda, in the Netherlands. I did not know it was Dutch. Is that where they make Gouda cheese? In the Netherlands? I think Gouda cheese can be anywhere, it is only named after the city where it was historically traded. Do you know when it originated? Was it recent or has Gouda been around for a long time? I don't know where it originated, but it was first mentioned in 1184, which makes it one of the oldest extant cheeses in the world. Yes thats pretty old. Older than American cheese I assume cause America hasn't been around that long lol.
However, the later versions are often a yellow hue due to the addition of annatto, a sweet and nutty seasoning added to cheddar and to Colby so that by the late 1800s American cheese was often simply called ''yellow cheese''.