Orange enclosure door interiors

Does anyone know where a specification for interior of the electrical panel doors to be orange came from? Was is a old NEMA or UL spec or maybe an automotive standard.

I would guess it could have been a warning color since an older panel would have 120vac on the door and open NEMA contactors inside the panel ready to zap someone.

I believe that it is an IEC (European) specification. Yet now most IEC boxes you buy have a galvanized backpan instead of the old orange ones for grounding reasons.

Its not the back of doors that have to be galvanised, but the backplane on which the components are fixed.

Did a job in Montreal recently where the customer complained because he wanted a 'nice' painted white backplane.

I installed a machine in a truck axle factory about 10-12 years ago, the specifications for the job stated that the Enclosure outside color would be safety blue, and the interior would be saftey orange. This was UAW manned plant, so perhaps it is/was an automotive spec.

We have done it for a long time. Predating me. I was under the assumption that it would be easy to see open doors from a distance.