Whenever i sit down, my left foot turns a purplish blue. all the time. my right foot does it to, but not as bad. once my whole foot and ankle was almost black. it doesnt stop until i stand and shake it for 10 mins or more. what could this be?

Time to see doctors: Purple or blue coloring to hands or feet usually means decreased or slowed circulation to the area. This can happen if the blood vessels get compressed or if the vessels tighten themselves and lessen the blood flow. Sometimes, blood flow will change due to nerve signals or chemical signals telling the vessels to constrict. It's time to see the pediatrician, who will likely refer to specialists.