do not know about the numbers/letters
but did read some time ago about the color
one of the top managers was riding a train out west and went through the wheat country.
thought the color of the wheat looked nice.
got back and directed they change the color of allis chambers from green to the orange color.
again, just read that somewhere long ago. but for some reason they did change color.
I think the ferguson paint buyers just painted their tractors whatever color that was cheapest that year during the late fifty's.
gray, green, cream, red.