Alphonse Karr bamboo, looking up into a clear blue sky. With blue filter (in software, of course . . . I gave away my collection of 52mm colored filters, because I have no more lenses that take 52mm filters). But this reminds me that I do have a polarizing filter that I don't use much. In truth, I can't remember what a polarizer does to b/w. Maybe tomorrow I'll experiment.
In a way, I feel as though I've cheated here, if my goal is to imitate what can be done in a darkroom. I can't think of a printing technique that can seriously darken just one color. When making the image, sure. Easy. But afterwards, I don't think so. Maybe I'm forgetting something. It's been years.
I have no idea who looks at this site, but if anybody who still works in a darkroom is looking, and knows how to take down a particular color from a b/w negative -- post a comment over at www.don-mitchell.com.