Norfolk Southern are painted black...but which one?

[Charlie B]

I have never had to use a primer on anything (model)I have painted, but I have only painted with black, Brunswick green (PRR black ) or Tuscan red. I do use red oxide primer as box car red with a gloss coat over it to decal over. Then I spay everything with dull coat. I would imagine having to paint light colors over a dark plastic would require primer, but I always hated to apply any more paint than needed because of lost details. N gauge has to be really bad where a rivet could be a mere suggestion of a bump.
Charlie