Hi Ian,
After speaking to an old chap who worked in the industry, i understood the original paint to be lead chromate. This could be supplied in green or brown and the chap suggested that as an apprentice, he spent so long mixing this cocktail that he still remembered the formula.
I was lucky enough that he mixed a 5 litre tin for me and also a pale green which some used as undercoat.
I have undercoated several parts which is an amazing hard finish. ( i actually dropped the fuel tank and the paint did not mark ! )
The nearest “feel” i could suggest would be red lead paint.
So i feel sure the original finish was indeed this paint.
It can be thinned for spraying but i used a very small brush and it flats very well indeed. No brush marks at all. But the guy has long retired and told me that the firm could do a batch but it would mean 100 x 5 litre tins !
Mvt type 28 shades of olive drab, pick one, type discussion.
For early war British green, cobbatobs light early war British green is right colour, for brown it's model shop leather brown number 64, for late war darker greens it's pick one you like, even the ones that look slightly blue.
Original finish varied, some of the 40/41 colours were garish and non military looking but they used what green paint they had.
Most nos parts are late standardised or refinished, as well you know.
