"N&W used a different red than PRR anyway (N&W used it before PRR ever owned any stock)."
Except on the three PRR 10-6 sleepers that were used in pool service with PRR, L&N and RF&P cars, all of which were in Pennsy paint and lettering style.
"PRR converted them to coaches and yes some ended up on MARC (I rode in some of them)."
Split between NJT and MARC. Several survive as coaches on the circus train, though now rebuilt to the point that you would hardly recognize them. RBBX also has ex-PRR 21 Rmt. sleepers, most of them also now heavily rebuilt.