My house is about 30 years old. I recently painted over exiting off-white trim in two rooms with white alkyd enamel. The new white paint turned yellowish tan in about 4 weeks.
I then painted over the discolored alkyd enamel with a coat of Zinsser shellac based primer. The bleed through continued. I then painted over the shellac based primer with an Oil Base primer. I waited two weeks, and then repainted the trim white again, this time with latex semi-gloss. The two primers did not solve the bleed through problem.
The trim along the floor is bright white (for now), and the trim around the doors and windows is a very noticeable darker shade of off-white. I have new carpet scheduled for installation in two weeks. I’m desperate and in need of some sound advice.