Thomas,
Earlier, the GTW had solid green day coaches on the commuters and the green/black coaches on the name trains. In the early '60s, they went to the more modern gray/black coaches. By that time, steam was gone on the Trunk. The mikes ran right up to the end of regular steam service (March 1960). With steam gone, the GTW had to use the more modern coaches equipped with electric heat. Some of the first generation diesels were equipped the steam generators but were being phased out. Of note, the GTW always ran their GPs and RS diesels long nose to the front.
For references, I would recommend the following:
"Evening Before The Diesels" by Charles Foss (great for steam and plant info)
"Grand Trunk Western Railroad" by Imre Quasler (early history of predecessor roads)
"Grand Trunk Western in Color- Vol 1 Steam and Green" by Jerry Pinkepank (great collection of photos)
There are others, but these are my favorites.
