Bartholian abscess ruptured on its own and it's draining more blood than pus (yellow). Why is that?

Frequent. Bartholin's cysts, if infected, contain pus but frequently cause bleeding when they rupture or are drained. If pus is present, a culture and antibiotic coverage may be indicated. If there are pockets of pus that do not drain, the abscess may recur. You should see your doctor.