I was looking for a netherite sword so I typed 'neth' then when I finished using it and went to put it back. I misclicked and put the sword back in the inventory while trying to delete it. After it was in my inventory, the 'neth' went green. Sorry if this was some kind of Easter egg or something but I don't know. This only works with 'neth' btw. There was white at the top so i didn't do anything like this '§a' or something.