I think that unless you are stopped for some other 'offence' and you have an attitude - the chances of falling foul on dark visor are negligible.
But - make sure that weather is not severely overcast or dark, and you you can mitigate any stop by having a clear visor in your tailpack, around your waist etc.
I hardly use a clear visor at all - going for black all the time.
Forgot one time, arriving in Caen at 21:30, severely overcast and rain, and with a helmet that changing visor was a chore.................... managed (just) the 10 miles to the hotel without incident..........