56 Squadron was involved in the trials to find a revised fighter day scheme at North Weald. I wrote an article for the Airfield newsletter about this. Part is reproduced below, which explains the reasons and what they tried....
From October 1940 onwards, RAF fighter pilots started reporting that the Temperate Land Scheme (brown and green) was too dark for the altitudes at which they were now flying and fighting. This Scheme had been developed for use at altitudes of 10,000 feet or lower. With fighting now taking place at up to 30,000 feet, and the RAF moving on to the offensive in the spring of 1941, effective camouflage at higher altitudes became more important.
On 26 March 1941, Fighter Command requested that trials be carried out by the Air Fighting Development Unit (AFDU), which was based at Duxford, with the help of the Royal Aircraft Establishment at Farnborough. The aim was to find a compromise scheme suitable for day fighters at all altitudes, as well as when dispersed on the ground.
Four different schemes were applied to the AFDU’s Spitfires. Initially, a two colour scheme was tried using a light grey. One Spitfire was painted in Sky Grey with an Olive Grey mottle similar to the Luftwaffe’s fighters (Scheme A). The underside was in Sky Blue. A second Spitfire was finished using a new colour for the undersides – half way between Sky and Sky Blue. The top surfaces were in the existing brown and green (Scheme B).
Neither of these proved to be satisfactory. The light grey was too light and provided too much contrast. So a third scheme was devised, which used Medium Sea Grey with Olive Grey on the upper surfaces and Sky Blue undersides and narrower yellow bands to the fuselage roundels (Scheme C). A fourth scheme was also applied to one of these Spitfires – Medium Sea Grey and Dark Sea Grey with the under surfaces finished in Sky Grey (Scheme D). Both of the latter schemes were much more effective at altitude.
During May, three 56 Squadron Hurricanes were flown to Duxford from North Weald to take part in further experiments – Z2697, Z2586/P and Z2767/W. A larger trial was then arranged using a further eight Hurricanes from the Squadron – Z2585, Z2697, Z2702, Z2992/K, Z3169, Z3324/F, Z3329 (shot down into Channel on 17 June when flown by Sergeant Richard Carvill, who was killed) and Z3352. These were painted in the C Scheme, and took part in a number of cross-Channel operations.
When the Squadron moved to Duxford on 26 June they were still using this experimental scheme. In mid-July, some of the Hurricanes had the Dark Sea Grey repainted in Dark Green, so trials continued to take place until the definitive scheme was settled upon.
On 8 August the Air Ministry finally distributed the new camouflage and markings regulations, which would be introduced from 15 August. These were known as the Day Fighter Scheme, and featured upper surfaces of Dark Green and Ocean Grey, which had a blue cast developed for these higher altitudes and was most probably Olive Grey renamed, along with Medium Sea Grey undersides. Sky codes, spinner and tail band were also specified, and yellow leading edges to the wings introduced for recognition purposes.
It remained in use for the rest of the war, and formed the basis of post-war camouflage until the introduction of the low visibility air superiority grey scheme in the 1970s.