Union Pacific 'Challenger' Production Models 

Aside from the paint scheme, the smoke lifters (commonly referred to as elephant ears) were the second standout feature of this model version. The black paint used on the upper features of the boiler and tender was commonly believed to be simple decorative accents, in fact, the idea was to provide a cleaner appearance for the locomotive in service due to the oil residue from the exhaust stack collecting on these surfaces, the dark color would tend to mask the oil film in between washings.