I'll have to consult, but the "bright orange" mentioned a few times is more likely what paint vendors and railroad lettering diagrams called "imitation gold." It was not a metallic paint like we imagine modern gold paints to be, but just a deep yellow pigment. This color was common on D&RG and RGW locomotives in the 1890s and early 1900s, before aluminum leaf, imitation aluminum, or white became the typical colors used.
Remember that black and white film does not record color the same way that our eyes do. Some films are infrared sensitive, others are ultraviolet, and depending on the process and skill of the developer this can cause light colors to turn dark or dark colors to turn light on the finished print. I have seen probably hundreds of photographs of steam locomotives from this period where the lettering does not show up at all because it was done in imitation gold and the film's spectrum sensitivity caused the yellow to shift dark to match the same shade as the black tender or cab.