Call me yellow if you will
, but I'd just turn it down and then turn it back up after they 'left the scene'.
There's no point getting into pointless pissing matches with cops, who are after all not chosen for their intelligence and sense of humour.
Yeah, I know the cops are in the wrong in this hypothetical situation. But if they want to pull you over, they will, and once you've 'made them' do all the work of pulling you over, they're sure to find some shit or the other to give you further grief with.