The Passenger Transport Executives (PTEs) were established by an act of parliament in 1968. Initially, there were five in England (Greater Manchester, Merseyside, Tyne & Wear, West Midlands & West Yorkshire) and one in Scotland (Strathclyde).
In the 1980s the railbuses and second generation DMUs were being built and some if these were assigned to the PTEs and gradually received special liveries to denote the PTE.
We see 141s, 142s, 150 s & 158s in these liveries between 1992 and 2000. I have no video or photos of the Strathclyde units.