Basic RAF camo schemes -
Early war - Dark Green/Dark Earth uppers, Sky lowers. (Battle of France Sky/Black lowers)
Intermediate - Dark Green/Dark Earth uppers, Medium Sea Grey lowers. (Usual SEAC colors)
Mid/late war - Dark Green/Ocean Grey uppers, Medium Sea Grey lowers.
Desert - Dark Earth/Middle Stone uppers, Azure Blue lowers.
Only a rough guide, individual aircraft varied on occassions eg the debate over the Malta blue spits, or the single sqn of pink Spit FR IX.s used on D-Day.
Good examlpe is the RAF P-51D I am doing. Was delivered from the USA in Olive Drab/Neutral Grey uppers, Light Grey lowers.
