Yes they were yellow with a red stripe along the bottom of the sides and aluminum end railings and platforms, as I recall..
C&O lettering of course.
I moved away from the neighborhood in late 1972,and the two PM cabooses were gone by then.I do recall seeing C&O "standard" wood and plywood cabooses sometimes at Rougemere ca. 1973-4
The only PM lettered car I recall seeing in that time was a black covered hopper at Rougemere (Dearborn MI) yard one day.
What is the address of the revived PM historical society?