Gerald - thanks so much for the input,
I treasure that website info.
Also I tried some RR colors iIhave and yours looks a lot like "burnt umber". I also tried "oily black" and "grimy black". They also had a nice look.
As you know, what you show looks nothing like any of the 3 "burnt iron" chips that I have seen, but I sure like yours the best. I will try your mixing suggestions.
BTW, is there any site where I can learn the proper terms for airplane parts? Unfortunately, instructions never seem to itemize.