Hello Andy Fox!
I realised that there was a change in the British national markings, too. In one of the Squadron/Signal books about the S.E.5a there was a profile of a fighter with toned down markings (dark blue instead of white) because it was used in the night fighter role. At the beginning of WW2 the markings were changed again (as you described it).
I think that today the national aircraft markings play not the important role (identification of enemy or own aircraft in sight) as they did up to the end of WW2. Computer systems and radar will identify the aircraft long before the pilot can see it with his own eyes. I think that today they are more symbols rather than markings.