"Some C G equipment and E-8 diesels were painted in IC Brown & Orange for pool service and I guess that an occaisional blue & Gay car might have operated in an IC train consist."
Possibly on the Seminole but definitely not on the City of Miami, which was one of IC's premiere trains. On the CoM all cars were required to be painted in IC colors if they were to run on that train, and this included some Northern Pacific Budd dome - sleeper cars that saw use from the early- to mid-60s... the cars would be repainted from NP TTG to IC colors with "Pullman" lettering and small NP initials and were then repainted about five months later when returned to the NP (at least one car was repainted into both schemes twice). All other cars from participating roads (ACL, CofG and FEC) carried the train's name on the letterboard and small initials and numbers on one end of the car, while some other roads sleeper cars that were assigned by Pullman to the train carried the same scheme as the NP domes with Pullman lettering and owner initials on the ends of the letterboard.
The Seminole, which use to be one of IC's premiere trains, was downgraded over the years but some effort was still made to match the IC paint. Both the CofG and ACL repainted Modernized heavyweight coaches in IC paint but instead of having the train name the actual owners' names were applied to the cars. Both roads had a number of cars painted to match the IC cars but only modernized coaches with the lightweight cars carrying the other paint scheme.
As for the CofG's two EMD E8As goes, they were delivered in Confederate blue and gray and only later were repainted into IC colors so that they could be used as pool power. Neither ACL and FEC did the same with their power, which typically had those roads power beyond Albany, Ga. The Central's E8s even made it onto other IC trains from time to time... a good match since they were already painted for the IC... and one even received the updated paint scheme of the mid- to late-60s with block lettering to match what was being done with the IC units.
As far as the sleepers go the CofG didn't have any lightweight cars and the ACL and FEC did not provide sleepers for the service though the FEC was in the middle of converting one of their boat-end Budd tavern - lounge observation cars into a smooth sided car for use on the CoM, though the project stopped with the strike that virtually ended passenger service on the FEC (save for one local passenger train each way on the line until around 1968) and the car was later scrapped. Shame really... would have been a great addition.
As far as MoPac's Slumbercoach, there was only one, Southland and it was later sold to the NP.