There’s room for argument over that Hurricane scheme: it was also seen on Fulmars which had no such airfield attack requirement. It makes more sense as a general means of reducing the aircraft’s visibility head-on, and would be equally useful air-to-air as air-to-ground.

Getting back to the original point: late in 1940 many of the tail bands and spinners were seen in Sky Blue rather than Sky, and the contrast with the undersides can be seen even in some b&w photos. At least one MU didn’t understand what was meant by Sky even into the autumn, but the use of Sky Blue seems to have ended by 1941 so presumably someone spelt it out to them!