A distinct historical phase in North American passenger rail when the newly formed national carrier operated a pooled fleet of inherited equipment. Trains ran with a chaotic mix of paint schemes from various predecessor railroads because the company had not yet repainted the cars into a unified livery. The resulting passenger consists looked like a patchwork of different corporate colors.
Heard on the job
You would see a green coach coupled to a yellow diner and a silver sleeper during the rainbow era.