It was in a collection of Army Council Instructions printed in 1943 which also lists other documents such as List of Changes that Armourers should be aware of as well as Equipment Regulations, routine procedure army forms etc. Specifically it expands on ACI 1356 of 1940 . I can send the whole document down the wire to anyone who sends me a email address. Originally 3000 copies were printed to be be sent to unit armourers and no doubt there were updates later in the war. It also refers to the ACI 361 of 1940 about Graphite grease and its use in the tropics. There's a table explains which of 4 types of grease or oil is to be used on which gun in which situation.
The relevant bit is
"Oil, low cold test, No. 1" will be carried in any " can, oil, M.G." of existing pattern. Cans used for this purpose will be painted GREEN by the units concerned to identify them from those used to contain existing oils.
Demands for "oil, low cold test, No. 1" and for the supplementary " cans, oil, M.G. " will be submitted by units and T.A. Associations ( for Home Guard units ) on or after 15th October 1940, on the scale of one " can, oil, M.G." ( of any pattern ), for each automatic weapon and 1/2-pint of "oil, low cold test, No. 1" for each gun or machine carbine a year.
Bare in mind the winter of 1939 /40 had been exceptionally harsh and we had just had our arses kicked in Norwayso failures in lubricating in cold conditions was probably on the minds of the powers that be.
I believe the Canadians pretty much followed our lead so if they had decided to change to plastic ( which probably wouldn't respond to paint very well at this stage ) it would be logical to order two colours of plastic. And Let's face it Canucks know about the cold! I'm sure they would have been pretty keen on issuing cold weather oil.
In a file at the pattern room library ( that was ) on the development of the Bren holdall there's a note dated August 1940 that mentions the need for carrying two extra lubricants , graphite Grease and " low cold oil"
ATaB
Tom
I'll have a look in the training manuals more in a bit.