Good news indeed! Thanks for passing it on.
One of the new items uploaded in November 2014 is a list of PC approved paints: actual catalogue numbers of the paint formulations various paint companies supplied for PC to use in different applications.
Including the infamous locomotive exterior enamel (which the list, b.t.w., calls "Brunswick Green"). It includes a sixteen ounce spray can (for touch-up, I suppose) from Sherwin Williams. If Sherwin Williams(*) still offers that particular shade, one way of answering the vexed question of what colour PC's locomotives really were would be to get a spray can, spray something (fender of car belonging to the guy next door with the barking dog that keeps you awake all night?), let it dry, and then look at it under different lighting conditions…
(*) Seriously off-topic, but did you know that "Sherwin-Williams" was a technical term in palaeontology? One theory about mammal evolution is that the main mammal groups -- including marsupials -- first evolved in the northern hemisphere and later migrated to places like South America and Australia where they are found today. This is called the "Sherwin-Williams model," in reference to the company's iconic "covers the earth" advertising image.