There were several, overlapping general reasons that WWII armored vehicles were painted a light color. One rationale for painted interiors was that it was an anti-corrosive measure. When you get down to brass tacks, the tank is a steel can with very little ventilation. Moisture trapped within the tank could cause rust, which in turn could inhibit operations of the vehicles' many moving parts. This anti-corrosive nature of interior paint also worked hand-in-hand with measures to minimize the impact of grease and other lubricants on the vehicle. The paint would allow for easier cleanup of these materials, although many tankers past and present will claim this was more of a Sisyphean task in operational conditions.

But the major reason why most tanks' interiors were some white or buff color was visual. Light colors reflect light better than unpainted metal or primer. Tanks had limited sources of interior light ranging from artificial lighting or ambient lighting from hatches or ports. The light interior colors maximized the limited light by reflecting it and made the tank a slightly less dark place to inhabit.