Allocation of RAF Unit Code Letters

British Aviation Colours of World War Two is a great book, but only presents part of the colours record – a lot has been found in the NA in recent years concerning memos and other communications clarifying some of the statements in the AMOs (e.g. the misprint for the overseas scheme as Dark Green and Middlestone, when it should have been Dark Earth and Middle stone)

Thanks for all three very helpful replies. I’m heading to the NA tomorrow, so will see what, if anything, I can find – any more help still welcomed …

This might be helpful…

The main publications were:
AMO (Air Ministry Order) A154/39)
Air Publication 2656A
Air Diagram No. 2390

and look here;
http://www.seawings.co.uk/images/colour%20charts/British%20Aviation%20Colours%20of%20WWII.pdf

And a couple of critical documents (namely the allocation of code son the outbreak of war) have, afaik, never been located

The magnum opus on the subject ‘Combat Codes’ , Flintham and Thomas , Airlife 2003 and Pen & Sword 2008 , refers to Air Ministry Order A154/39 and Secret Document SD110 in Chapter 2 of the book which is entitled ‘An Introduction to Unit Markings and Codes’ .
Might be of use ?