Many former New Haven Railroad passenger cars were fully repainted by Penn Central following the takeover. Most of this activity appears to have happened during the first year or two and was more or less abandoned (at least as an organized effort) after Penn Central went bankrupt in 1970.
Although many FL-9s remained in tattered and patched remnants of their original NHRR red-orange, black, and white colors through Conrail, Penn Central fully repainted a large number of them black using a variety of marking schemes. In March or April 1969 Penn Central sent a train composed of former NHRR coaches and two FL-9s out on a tour of the New Haven Region. There was a short article about this in an issue of the PC's original Penn Central Post employee magazine (not to be confused with the current PCRRHS publication). Basically, this train of fully repainted and refurbished equipment was put together as a public relations exercise to show that Penn Central was making improvements to passenger service on the New Haven Region. At that time, there had been many passenger service cutbacks and the general quality of service was deteriorating, etc., so the train was put together to provide the impression that Penn Central was committed to improving passenger service.
Former NHRR passenger equipment retained by Penn Central that was repainted were done up in several different schemes. For example, some of the Osgood Bradley lightweight coaches were painted green and had white PC logos painted over the trucks. The Pullman Standard streamlined coaches got green window bands, black roofs, black and white pre-printed fiberglass number boards, black and white fiberglass pre-printed "Penn Central" letterboards, and either got black PC logos over the trucks on aluminum panels (pop-riveted over the original NH logo plates) or had the NH logos scrubbed off and had the PC logo painted directly on the old stainless steel logo plates. Other types of stainless steel sheathed passenger cars got variations of this treatment, some with green and white logo plates, some with green and white letterboards, name boards, or number boards, some had their NH logo plates scrubbed off and PC logos were painted on the window bands, etc. There were many variations.
To my knowledge no ex-NHRR RDC got a green or red window band. What happened was that early in 1969 some former New Haven RDCs had green paint crudely applied to their ends up to the level of the red-orange stripe to cover the New Haven NH marking. Later on, they all got a black, white, and red zebra stripe pattern on their ends similar to what the New York Central had applied on their RDCs. The ex-NHRR RDCs given the Penn Central treatment had the script monogram on their sides covered with an aluminum or stainless steel panel that had a black PC logo on it. The "New Haven" lettering on their letterboards was scrubbed off, and they generally got new black and white number boards.
When I was a kid in the Boston area during the Penn Central era I remember local passenger trains having a mixture of PC green painted former NHRR lightweight coaches, former NHRR streamlined coaches with PC green and NHRR red-orange window bands, and former PRR P-70 heavyweight coaches in tuscan red and PC green all mixed together. By the time I started train watching in earnest (1972-ish) the former NHRR black and red-orange lightweight and heavyweight cars were no longer in service (or if they were I never saw any). As the 1970s progressed these cars became increasingly tattered looking. For example, it was not unusual to see former NHRR lightweight coaches with red-orange window bands, New Haven letterboard and number boards, and one or more of the NH logo plates removed. You'd also see some cars with PC green window bands and some combination of the PC letterboards, number boards, and logo plates missing.
They were certainly interesting times.