I broke my ankle and got the cast off four months ago but my ankle still swells up easily and turns deep red and blue. what's wrong with it?

Maybe: Venous insufficiency or damage to the lymphatic system.

Vascular evaluation: Swelling after a fracture can last up to a year any swelling past a year is permanent. "dependent rumor" which s what you may be describing often is a sign of a venous problem and may requires a vascular doc to check it out to see if there is a need for treatment.