A Question about Running Board Colors

So this is something I've been thinking/wondering about recently. It started off more as a conversation about color and paint schemes on model locomotives, but it made me wonder about the prototype(s). None in particular in that conversation, but what about on the Colorado narrow gauge roads?

Someone once mentioned to me that there was a certain paint that was like a cross between barn house red and rust. (An oxide color of some sort apparently) But it was supposedly very durable and was often used on tender decks, cab roofs, running boards, or anywhere that there would have been heavy foot traffic. This I think was popular around the turn of the century, but what about the 1870s/80s? Were running boards on early locomotives just painted black? Varnished? Or where then treated/painted in some other way?