In discussion with mechanical dept people at BHM the green paint starting top disappear after WWII.
During the war they wern't too fussy on green over black. Paint was what you had in stock to put on.
Existing stock of green paint would of course get used up. Paint was still paint! This was the case over the system from what I understand.
I think the 340 was one of the last of the "chippies" to have a green jacket, wasn't it?
Once steam was realized to be on the way out things weren't kept up as they had been.
As for the red cab roof, that is an odd one. The tape of it is a one of kind. Must have been short of paint or maybe someone just came back from seeing a road that used red paint for cab roofs (like the CB%Q & C&S)and decided to "try it out".
Chris