I wonder if grue was taken from Nelson Goodman's Fact, Fiction, and Forecast. https://en.wikipedia.org/wiki/New_riddle_of_induction

Nyet. Jack Vance created grues in the one of the Dying Earth series books.

Yes. Because it is pitch black and therefore you can not determine it's color (plus, the fact that you haven't been eaten by one yet does not justify the conclusion that you won't be). It's also a play on Gardener's "unexpected hanging paradox".

Love it. I use a grue reference on 404s to my blog.

https://mordenstar.com/zork

If this predicament seems particularly cruel, consider whose fault it could be: not a torch or a match in your inventory.

MC Frontalot - It Is Pitch Dark

https://www.youtube.com/watch?v=4nigRT2KmCE

Featuring Steve Meretzky!

https://en.wikipedia.org/wiki/Steve_Meretzky