Burlington Northern basically just carried on the service of GN, NP, CB&Q & SP&S until Amtrak took over, and by BN's time those services were somewhat reduced. I think the cars that were painted Cascade Green with the white "hockey stick" were in the minority, though a few experiments were painted before the merger, so they were around from the beginning, mixed in with GN orange & green and big sky blue, NP green and CB&Q stainless steel. With only a year before Amtrak, BN didn't have a lot of time to paint, so a lot of stuff wasn't, but BN was faster with repainting than BNSF has been; all merger locomotives were either repainted or retired by about 1980. Passenger locomotives were ex-CB&Q E7s E8s & E9s, ex-GN E7s SDP40s and SDP45s and F-units from GN, NP & SP&S. As with cars, many of the passenger units weren't painted before Amtrak, but for those that were: The Fs were Cascade Green with the "hockey stick" and the SDPs were painted like freight units. Most E7s weren't repainted. The CB&Q Es had unpainted stainless steel sides and stayed that way with BN, (until rebuilt for commute service). Various techniques were used on the cab: silver with black stripes, silver with green stripes or a green cab with white stripes like the Fs, but stainless sides. Lettering was usually black, sometimes green. Some Es got BN lettering but kept their CB&Q nose striping. Stainless Steel ex-CB&Q cars also got black lettering.
As for trains, Western Pacific ended their portion of the California Zephyr just a few weeks after the BN merger, and BN reduced their portion of the service as well. Before BN, the Portland cars from the Empire Builder and North Coast Limited were put into a single SP&S train (SP&S used their own power, head end cars, diner, lounge, and coaches for local passengers). I think the same arrangement continued under BN.