Dan,
The old colour debate can go on and on for any make of farm machinery and tractor apart from dare I say it John Deere who have not changed their colours throughout the years, most other manufacturers have been swayed by factors of the era to change their machinery colours and Massey have certainly been high up the list on the amount of changes and encompassing different companies they bought to get a certain machine, hence many colours.
Getting back to your question about green, my opinion it was one of the colours used for horse drawn implement's way back in the late 1800's possibly even before Massey and Harris merged and way before any signs of the internal combustion engine or tractor was even thought of, I also think there was many different shades of green, as well as light blue on some early grain binder parts, together with the darker burgundy red and cream, I must say a combination of these colours makes an implement's appearance more appealing. Plus I am sure the different shades could be down to cost and different suppliers who ever was the cheapest at the time.
All the old guys that built and worked these early machines of the late 1800's and early 1900's are no longer with us, they would of known the answers to our questions and that's why its our job to document history we know of today, otherwise its lost for ever.
What is other Massey Collectors views on the paint schemes?
Malcolm.