In particular I don’t know what to think of the gray wire. Most resources online suggest gray is neutral. If I treat gray as black I would go black to black, grey to red, red to red/white, green to ground based on the instructions.
That's an off-spec black
That "gray" wire is really a black wire that is off-spec a bit on color, as NM does not come with gray wires in it (or pink for that matter, so the "pink" wire is really a red wire).