Here's some info on the Fairey Battle, which also applies to a number of other early RAF types (Wojtek kindly scanned the pictures accompanying the article and will post them in a seperate post - thanks mate!)
RAF Battle Camouflage and Markings
By Ian D.Huntley (Scale Aviation Modeller International – June 2001)
Between the Wars Light/Medium Bomber Finish
The prototype Battle K4303 (F.2121) appeared first in March 1936 in unpainted form, and with red primer (shrink dope) on fabric control surface areas. After it's first flight it was to receive an overall Aluminium dope covering in a very fine matt form, being the peacetime finish for all but heavy Night Bombers and Training aircraft, but already 'camouflage' diagrams were being prepared by the Ministry for all new Expansion Programme types. The Alumimium top coat medium was in fact the new Cellon 'X' finish. National markings were in Bright Red, White and Blue, positioned at the extreme wingtips, and on the fueslage at the wing root fairing location.
The registration was marked in Night in eight-inch characters on the rear fueslage and on the rudder surfaces. Much later it was applied in large 36-inch characters on the undersurface of the wing parallel to the trailing edge line. Standard W/T bonding marks, component serials , factory inspection marks, AID stampings, and finish markings, appeared in all relevant locations, also in Night.
Strangely, and possibly with the exception of the Belgian order for 16 Battle airframes, the common Fairey practice of marking the factory 'F' number adjacent to the fueslage registration was not applied to the Battle, the 'F' number appearing only as a stamping on an identity plate within the pilot's cockpit.
Internal finish including cockpit and wheel well areas, was a Grey Green colour, being a commercial metal primer Cerrux MP4, a light khaki-green close to FS 595a 34259.
Appearing in much modified form and in public for the first time in June 1936, K4303 received the numeral '4' in Night ahead of the fueslage roundel on each side as seen in the New Types Park at the RAF Display, Hendon.
Complicated Camouflage Designs
Camouflage in a new matt material, was an entirely new issue for the Hayes drawing office who were presented initially with a Systems Installation Scheme (SIS.10) issued by the Royal Aircraft Establishment (RAE), South Farnborough, in about March 1936, showing in very precise detail a two-colour, very convoluted demarcation, upper and side surface pattern, illustrated in a number of colour combinations, showing Land Scheme (L.1), with four schemes; A,B,C,D.
The complication was that although only one pattern and it's mirror image (handed) was drawn, with the transposition of the two colours, two further schemes emerged making four in total. Hayes, after discussions with Stockport, was fairly quick to point out the possible production bottleneck which might result iin dealing with four schemes in the paint shop, but were informed in a subsequent reply (Circular Letter No.457: Dated 9th April 1936), that in a coloured Air Diagram issue expected to become available in may 1936 as Air Diagram (AD) 1158, and to be titled 'Camouflage Scheme for Single Engine Monoplanes – Medium Bombers', that two of the schemes were only considered as 'optional'.
These were however faithfully redrawn as Works Drawings giving Scheme 'A' and 'C' for aircraft with even registrations, and Scheme 'B' and 'D' for odd registrations, and submitted back to the Ministry for approval. However in the Hayes Drawing Register only two schemes can be accounted for, and certainly by early 1939, Issue 2 of the (coloured) Air Diagram only Scheme 'A' and 'B' were shown, evidence being borne out by contemporary photographs.
Production Paint Shop Problems
Handing of the pattern however did not follow precisely the odd and even sequences as machines were subsequently painted two at a time with identical patterns/colours. Again, during production machines became out of factory sequence numbering, and although handing continued that too often ran out of sequence, an event that also applied to many Austin-built machines.
An interesting feature of the camouflage was that the area of decking underneath the glazed canopy section between the cockpits was always in Dark Earth regardless of the handing.
The undersurfaces were in Night initially restricted almost entirely to the undersurface areas with hardly any Night showing on the lower side surfaces. Later the Night was extended upwards to a 60 degree angle of demarcation which also included much of the radiator bath sides. The regristation was marked in large white characters angled to follow the trailing edge line as in the prototype, though with later production aircraft the characters were set in a line perpendicular to the machine centreline.
With camouflage came a different location for the wing roundels, now set inboard from the wingtip at some one third of the span from tip to centreline of the machine, and whilst the standard Red, White and Blue roundel remained as the national identity marking, camouflaged aircraft had the addition of an outer Yellow ring added at the same band width as those of the existing colours. These markings were also in a matt finish, the camouflage colours being of dull form.
Internal finish was Grey Green primer including the cockpit areas, with instrument panels and consols in Night. The pilot's seat was an anodised aluminium finish with a brown leather backrest.
No reference has yet been found which details whether the prototpe K4303 (F.2121) , or the first production machine K7558 (F.2316) received camouflage first? The latter machine bearing the scheme took to the air for the first time at Ringway on 14th February 1937. Likewise no photograph has yet been found which showed the prototype in camouflage?
Service Markings
Entering service with No.63(B) Squadron RAF in May 1937, the unit, which did not have it's full compliment until the end of the year, was closely followed by No.105(B) and No.226(B) Squadrons. These early units initially marked their identity in approximately 15-inch white numerals on fueslage sides midway long the canopy length, adding a smaller 6-inch sized individual aircraft letter, first on the cowling, and later to a 15-inch size on the fueslage side well aft of the roundel.
The style and form of these markings roughly followed a style of character issued by the Ministry in May 1931 though the proportions were not closely followed. Thus by the early Summer of 1938 the Ministry set a standard form which for the Battle amounted to 27-inch characters with the unit numerals ahead of the fueslage roundel and individual aircraft letter aft of the roundel. This edict applied also to heavy bomber units with proportionally enlarged characters. The colour used for these markings was Medium Sea Grey.
A further service addition was often that of 'FIRST AID' in two lines, in some two-inch high Red characters on the the fueslage port side just below the gunner's canopy.
A requirement was the addition of an 18-inch square gas detection paint applied generally on the rear fueslage decking just ahead of the fin marked with the diagonal of the square parallel to the fueslage centreline, the square was often thinly outlined in Night.
Hardly had this overall form taken effect when the Munich Crisis of August 1938 set the precedent that all operational aircraft of the RAF replaced any evidence of unit identity with code letters, and had changed national identity markings to the Red and Blue (night roundel) form. Registrations were also painted out. By October when the crisis had passed a return of registrations was made, but as far as operational aircraft were concerned those on the underwing were not replaced.