[Nicholas]

"try this: open the images in Adobe Photoshop and use the 'Auto Contrast' and 'Auto Levels' commands to correct the images.
you will see the underside is Gray , not Green"

Yes, I know all about correcting digital images and the results, thanks. The undersurfaces are a very pale blue-green - not a light grey. I have no doubt that they can end up looking more like light grey using Photoshop, especially using the auto correction parameters and given the colour space occupied, but that is not a reliable approach. When it comes to colour the "Mark 1 eyeball" is perhaps the least reliable methodology! It is subjective and dependent on colour perception. Colour science and colour facts are perhaps preferable to colour opinion. Btw Sky is not "green" but rather a very pale blue-green very close to the "grey" colour space.

It is better that we consider all the available evidence. Whilst it is certainly true that not all specifications were followed and there are many anomalous examples, they do provide evidence of what was intended and required. In fact the evidence suggests that AMO's were usually closely followed and that deviations were often the result of misinterpretation and/or specific unit/theatre changes. In the case of the BPC and American contracts the requirements were more closely followed as there was a comprehensive inspection and acceptance process that included the camouflage paints being used in American factories.

You identify the colour used as ANA 602 Light Grey but in fact on 19 Jan 1944 the Technical Sub-Committee on Camouflage report on ANA colours was revised as follows:-

"That Navy Gull Gray Dark be adopted as standard and the British Sea Gray Medium and Navy Light Gray (ANA 602) be eliminated."

However, Sky, required by the FAA as part of the Temperate Sea Scheme (TSS), had been accepted as a standard ANA colour and continued to be so, long after it was no longer required for RAF aircraft:-

"(13) That the British Sky Type S Gray be accepted as standard"

The word "gray" was later dropped from the terminology but as Dana Bell records "The color which became ANA color 610 was the same pale greenish gray called Sky in the UK." In fact the US substitute Sky paints varied from the original AM RAE swatch and were based on the Du Pont 71-021 Sky-Type S Grey swatch provided to the AM & BPC and in turn cited by them to US manufacturers as a sample to match against - a fact revealed by Dana Bell himself. This was a very pale blue-green, exactly similar to the appearance of the undersurfaces in the colour photographs, but could vary in appearance from a very pale light blue to a colour much more like Sky as a result of the imprecise paint formula and the use of different white pigment types.

Then we have the January 1941 report of the Chemistry Department of the RAE which succinctly summarised the British approach to aircraft camouflage, listing only three colours (at that time) for the undersurfaces of camouflaged aircraft (of which none was a light grey):-

"1. A light duck-egg blue (standard 'Sky') for use against day sky backgrounds in temperate climates for both land and sea aircraft normally operated at or near cloud level."

So the empirical and other evidence is as follows:-

1. BPC/AM & FAA wanted Sky undersurfaces (AMO 864 & Others, + correspondence & memoranda)

2. ANA charts continued to include 610 Sky but dropped 602 Light grey (correspondence and amendments)

3. Colour photographs, before manipulation, appear to show an undersurface colour exactly like the US manufactured versions of Sky, aka Duck Egg Blue or "Duck Egg color" and which matches the extant, measured swatch for Du Pont 71-021 Sky- Type S Grey (that is not to say the paint used was Du Pont - it was just used as a convenient sample by BPC & others).

4. When the original factory applied paint on KD431 was examined, the undersurfaces of the tailplanes (in TSS) were found to be Duck Egg colour - the report states that "this paint, having been concealed from daylight for over half a century. now provides an excellent primary-source colour reference for the Second World War temperate colour scheme of olive green, slate grey and sky ('duck egg') applied to British aircraft".

5. Page 78 of Ron Belling's 'Military Aviation in South Africa' re the colour scheme of Corsair 6C - JT324 which "clearly illustrates the contrast in colours when US-built aircraft were finished in approximate BS equivalents. The top surfaces are Olive Drab and Sea Gray and the undersurfaces Sky."

6. Part Three of Ian K Baker's 'The History and Development of Olive Drab and Other Camouflage Finishes', specifically the sections entitled 'Sky or Light Grey?' and 'Olive Drab with Sea Gray'.

7. Nowhere, in any primary source AM, BPC, RAE or RAF documentation, or in the colour notes recorded by contemporaneous eyewitnesses like Ian D Huntley and M J F Bowyer, are there references to "light grey" undersurfaces on US export aircraft intended for the RAF or FAA.

AFAIK there was no requirement for the Temperate Sea Scheme to use "light grey" as an undersurface colour and there is no documentary evidence (?) to suggest why Corsair aircraft should have been manufactured with light grey paint applied to the undersurfaces instead of the Sky/Duck Egg colour.

What seems to have happened is that some US modellers may have become confused over the Temperate Sea and Day Fighter schemes, assuming that the Medium Sea Grey undersurfaces of the latter were required for Corsairs, especially as the upper surface colours appear to be the equivalent to Dark Green and Ocean Grey. But this is also part of a general trend to promote a light grey undersurface colour for many US export RAF & FAA types, apparently with little evidence to support it.

So we are being asked to ignore all the cumulative, holistic evidence summarised here, abandoning the principle of Occam's Razor in the process, in favour of an individual and subjective visual perception which results from a commercial software paint programme auto-correct of a digital image posted on the internet? What I think you might ask yourself is why should light grey have been applied when the requirement was for Sky and Sky paint was included in the ANA chart and list?