Even if consulate/diplomatic car, it could be dangerous for its owner to visit Marseille with such plates, as football/soccer supporters from this city don't really like the Paris Saint-Germain (football team from Paris) and could think that it is a provocation

(I'm half joking, in fact, as each match between the 2 teams turns really violent in and out stadiums, and "extreme" supporters seem often to have forgotten they were provided with a brain at birth...)