So it said "blue" in the hover-clue, then it says "green" here, and then I check it again and it has the option "grue". Is that a thing now?
High Valyrian, like some other languages, has a single word for green and blue: https://en.wikipedia.org/wiki/Blue%E2%80%93green_distinction_in_language
Having a single word for blue and green is one thing, but this "grue" business in English is new.
It's a recent, self-conscious coinage, used specifically to discuss things like words for blue-green in other languages. It was, I think, borrowed from Nelson Goodman's 1955 grue and bleen thought experiment in philosophy, where it has a different meaning (which see). The linguistic meaning was used in Berlin-Kay's seminal 70s work on color words in different languages.