Hi Franek. This is the order from the M.A.P. to R.A.E on Aug. 11 1941 to change to a "Mixed Grey" replacing Dark Earth (but note reference to "Ocean Grey" before it was officially adopted); a memo from HQ Fighter Command to HQ Maintenance Cmd. dated 21 Aug. confirmed it for Day Fighters.
Air Diagrams affected were AD.s 1159 and 1160. Actually there was memo from HQ Royal Observer Corps to Observer Groups on the 8th. noting Sea Grey Medium undersides to replace Duck Egg Blue.
Regards
Nick
camouflage-change by
Nicholas King, on Flickr