Back in the 1980s, the Southern Pacific and Santa Fe railroads were facing competition from much larger railroads, like the Union Pacific and Burlington Northern. The two would attempt to merge, and long story short, it was denied by the Interstate Commerce Commission. However, the two were so confident it would work, they created their own livery, nicknamed the 'Kodachrome' due to its resemblance to Kodak camera film boxes at the time. If you want to know more about the whole merger, there's a documentary on YouTube that goes over it
