re #15
Got it from here..
https://ww2aircraft.net/forum/thread...des-why.22071/
"It was used from 1938 up until June 1940, half white half black, for observation of friendly aircraft from the ground. Remember that there was no country-wide ground control radar. Radar only worked looking out to sea, or at higher altitudes, initially only being placed on coastal sites . Tracking over the land, friendly or enemy, was down to the Observer Air Corps.
It was replaced by Sky undersides, but in November 1940 the black wing was reinstated."