For cellulitis how long will discoloration last?

Possibly months.: If it is true cellulitis it may be red for a while and then fade. If it is venous dermatitis is will never improve, because that will cause hemosiderin staining of the leg. This is when the leaking veins carry the red blood cells out into the surrounding tissue and when they die they leave their iron deposits in the skin and it results in a permanent brown discoloration of the legs.

SLow change: As injured skin heals, the body creates inflammation to do so which means fresh blood goes to the area and with it, many kinds of healing factors and cells. One type is called melanocytes which carry our skin pigment melanin. A healing occurs, these cells get deposited in the area and give it the brownish coloration you see. Over time, there will be some fading as the injury matures.