Lee I think the white tips and the white edging to car wings was to give some indication of your presence during the blackout periods in England. Not so necessary for front line motorcycles where a more cammo effect would have been sought. But
White mudguard tips were sometimes seen on BEF motorcycles during the phoney war period and four-wheeled vehicles also often had the front left-hand wing in white (the off-side in France).
In the UK, it was often done by private motorists and cyclists.
I have the impression that later in the war when air superiority had been obtained, it was most often done by CMP Traffic Control. It fitted in nicely with the white blancoed webbing and made them stand out in traffic
I suspect that by 1944, the military was foregoing the application of gas indicator paint... I have no real knowledge on this; best to seek another opinion more expert than mine!
WD instructions for gas paint application did call for a circle or patch of paint on the front mudguard as well as the headlamp..Whether it was actually applied..and if it was what form it took, is another matter!..I must admit from a seated position on the bike you can't really see the top of the mudguard so maybe it was concluded there was not much point in this and it was generally omitted....Another interesting point..did the Brits always use their own yellow (early) or mustard coloured (later) gas detection paint or did they use the green American gas paint as well?..
When or if its use stopped it is another thing for consideration..it could be argued that as the Germans situation worsened in the latter stages of the war, in desperation they might have been more inclined to use gas......Ian