I once drove my players crazy by describing the walls of the scary tomb they entered as red. And then repeating that as often as I could. "Red walls. Red. Red red red red red. Blood red. No, you don't find any traps. Red walls. Like a sheet of blood. Red blood. Ahead of you, you see a passage leading off to the red, I mean right. It's the same width as the passage you're in now. Yes, the walls are red. Did I mention red yet?" And so on.