Re: Why black?

I think that it has a lot to do with how the oxide red paint is produced. The original oxide reds came from Iron Oxide deposits, Red Ochre if you prefer, that were mixed with a light oil for application. When this dried, adsorbed, or did whatever it did, it provided a naturally resilient paint. The iron particles can't fade of decompose because it is a rock, it could continue to oxidize but the fact that it is covered in a thin layer of oil slows this process. The original UP oxide red came form a deposit outside of Rawlins if I remember right, the UP owned the land, so they just dug it up, ground it up, mixed it up, and sprayed it. Think of some of the narrow gauge boxcars that you have seen with no lettering but the base coat is still in pretty good shape, the lettering decomposes but he base oxide layer is more resilient.
Paul