> "after looking at blue British detector paint in the early 1940s" It is odd that the article doesn't delve into that point more. In the early stages of the

> "after looking at blue British detector paint in the early 1940s" It is odd that the article doesn't delve into that point more. In the early stages of the war, actually from mid-1938 onwards, British aircraft and vehicles had 'gas detector' panels which were squares paper soaked in the detection paint and taped-on. It was usually yellowish with one on the wing or the fuselage-spine of aircraft: https://ww2aircraft.net/forum/attachments/a380efa1d53530a5-jpg.428273/ https://ww2aircraft.net/forum/attachments/a380efa1d53530a5-j... Those fell out of use from late 1940 due to the low risk of gas attack and production ended in 1943. Just as the USA was starting production of its M5 paint!