I will add my two cents to this discussion. At the main library in Philadelphia there used to be a great picture book named Twenty Colorful Years which showcased all SEPTAs transit liveries. I don't remember if it included pics of the post private Bluebirds and MP54s.
Anyway, hers the lowdown on what I remember from riding the system and what was in the book.
When septa first took over the city division, no new paint jobs were applied. Just removed the PTC wings and slapped on SEPTA in plain letters. The SEPTA symbol was not developed until after the Red Arrow accqusition. If you notice the SEPTA symbol "S" is actually two arrows intertwined. Closely resembling the arrows used in Red Arrows emblem. Before repaints, SEPTA applied it's new symbol to all vehicles. In the book you see alot of red arrow trolleys still in thier faded red and cream with SEPTA's new emblem. This is also true in the city, lots of pics of trolleys with the green and cream plus purple belt rails with the emblem.
Septa's first repaints were in thier original colors. This is why on the Red Arrow and P&W you saw cars in the Red Arrow scheme well into the eighties. The only difference is the "red" SEPTA used was actually a very deep Maroon. Also the "cream" SEPTA used was not very creamy, it was more of a dull bone white. Original repaints were done on the city side also, however the purple belt rail was eliminated. SEPTA soon decided that a new image had to be made to sperate dit from PTC and Red Arrow. This is where the experimentation begins. The first color scheme tried was the Gold livery. This livery actually is my favorite. The few cars that were re-painted in earlier in red were not painted in this gold. The main body of the car was painted in gold foil paint. On the belt rail was applied the deep marroon. The window area was the same dull white. And the roofs were silver foil. The only differences were the 80s got silver roofs, while the St. Louis' and the Brilliners got Black roofs. None of the P&W cars did however. The city divsion painted 2 cars in this scheme, however the belt rail was red, not maroon and one of the cars 2176? also received experimental air conditioning.
Septa thought it had found it's new identity, until the cars started to get dirty. Also during this trail time for the gold livery, more city cars were painted in the green scheme. Also, one car on the P&W and one car on the city side were painted in an experimental tan scheme. The gold was liked better, so the gold won. The P&W car was reapinted, the city car kept the tan livery until retirement. Also, Septa had two experimental schemes on the city side. One was Yellow, marroon belt and white roof. The other was Bel-Air blue, and a white roof. Both of these cars stayed in these schemes until retirement.
With the failure of the gold scheme, a new scheme had to be implemented. This was the famous Gulf Oil. It was used in different combos on all 3 systems. On Red Arrow, the 80 series received silver roofs, while the St. Louis' and the Brilliners' received blue roofs. On P&W there were some variations. All had silver roofs, but some had purple belts, the others blue belts. On the city side, there were also some different variations... Most notably the doors. In my opinion, the Gulf oil looked best on the Air-electrics, especially the rear view. So up until 1980-81 when the new LRV started to arrive the whole SEPTA system was a non-standarized clorful array of pre-SEPTA, gold and Gulf oil. The introduction of RED-White and Blue on the LRVs made it to some of the PCCs although Gulf oil was still seen well into the eighties on the city side. P&W also had a variation of Red-White and Blue, but again Red and Cream and Gulf oil survived until retirement.
Hope that helps.
900,000 tons of steel, made to roll
The brakes don't work and this grade's so steep
her engines sure to blow...
900,000 tons of steel, out of control
She's more a roller coaster, than the train I used to know.