The passenger car is the "B-3" not the B-2. But you already knew that. The B-3 was painted up Grande Gold with the twin black stripes and named "General William Jackson Palmer" ( not to confused with car B-7 which was also named the "Palmer" in the 1960's and still carries that name), for the 1949 Chicago Railroad Fair. At the Fair, The B-3 performed along with #268 and a couple of excursion cars made out of high side gondolas. When the B-3 was returned to the rails in 1957, it got the name "Nomad" - named after Palmer's standard gauge private car in the Rio Grande Western.
I guess the B-3 painted Gold would be the first narrow gauge passenger car painted as such, predating the cars dolled up for the Silverton Branch in 1950.