Gary.......prior to the adoption of camouflage ( Dark Green -Dark Earth ) for the topsides in 1937-38 the external finish of prototypes was left to the contractors concerned , as Waynos says no authorised schemes.
The attached is the relevant memo from the AM as to the first 3 schemes approved , for Hurricane, Battle and Spitfire. Note the unusual finish chosen for the Spitfire though it was first flown in primer/ polished cowlings.
The stipulation was that the adopted colour was to be a light shade with bright insignia and black details.
When camouflage was introduced as standard on production lines, prototypes were to be DE/DG above and yellow below as defined in the above posts and specified in AMOs.
I'm sure Antoni is right about the circle "P" marking in yellow ( size as fuselage roundel) from 1941.
The "Aluminium" finish comprised aluminium dope on fabric with polished metal cowlings.
Nick