I had an "in the white" Bess I used to experiment on. The blessing of in the white is that you can always get it back to where it was. I noted the description of one product was "Plum Brown" and I thought "why not try it?" Sure enough, plums darken the steel. Apples work to, as does Clorox or Hydrogen Peroxide on a cotton rag. The latter two very slowly and I used then to "touch up" where I hard to buff out dark stains and tone it in to blend with the rest.
I actually found in the white to be very easy to keep ahead of.
My iron mounted Lehigh was over hot rust blued/browned (to the point of minor pitting) and then carded (wire brushed) back to a gray finish, repeated, then dipped in hot bear oil and baked. Sort of a deep weathered patina.
The bear oil coating has worn off the exposed metal but (I hope) it is protecting the hidden metal well enough.