There are some sound observations and good tips in this thread from a couple of pages back,
That Old Sinkin' Feeling.
There is some mention in there of just getting rid of the culprit pigments. Peggy Baumgaertner, for example, talks in her videos about having done just that.
I've had my best luck here with just rubbing linseed oil over the area with my fingertip, then wiping off the "extra."