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This is Dr. David
it does sound like you have bad venous status issues in your lower leg, ankle which can cause dark red skin changes in your lower ankle.
the pain can sometimes be from cellulitis infection of soft tissues.
you need to ask your doctors if you have celluliits and if you need a course of antibiotics to help clear up soft tissue infection.
you may have to cut down on salt intake which can cause you to retain more fluid and have more venous status in your legs.
when you elevate your legs and ankles above your heart, you may need to try to ice the foot and ankle as well to decrease swelling and pain.
you should try compression stockings as well which can help squeeze out excessive fluid out of your leg.
regular walking and exercise could help push fluid out of your leg as well
let me know if you have questions.