Does this practise apply to the early war buff coloured bombs?
The British Explosive marking scheme was adopted by the British Army and Royal Navy in the mid 19th century as a standard Marking system for all Military Explosives. In accordance with this system all High Explosive Shells for Army Artillery and Naval guns were painted in the base Light Buff colour for easy identification with a system of coloured rings to identify role and filling.
This Marking system was carried over to the first Aircraft bombs in 1914. And did not change until early in WW2 when the base colour changed to Bronze Green for I believe ground camoflage reasons. (Incedentally, Artillery HE shells remained Buff as they were delivered mainly in boxes!) The colour ring marking system did not change.
The ring marking system was continuously added to as new propellants and explosive fillings were developed and used in UK ordnance, but the basic Marking system remained in use with the British until 1964 when the UK adopted the NATO standard explosive marking system as used today.
The British Aircraft Bomb base colour (Bronze green) changed to Deep Bronze green, along with the official British bomb single point suspension system to the NATO standard twin point, at the same time.
This change to NATO standards was not an overnight change, the bombs were repainted on the normal servicing cycle and the suspension system modified on bomb refurbishment, and of course on new build bombs. this change process probably took about ten years in all.
I think the last RAF Aircraft types in service that used British standard single point bomb suspension were Buccaneers (in Internal bomb bay) and Hunters.