The question is pretty much summarized by the title. I'm in Vietnam, and a particular historical site is consistently called a particular thing when referred to in English. I'm trying to figure out why it's called that. Is such a question on topic?
Specifically, I'm trying to find out why the "Purple Forbidden City" in the Imperial City, Huế (link to wikipedia), is called "purple". I just don't know if I should be asking here, or if maybe I should try the "Linguistics" SE.