See your doctor. Leg swelling can be secondary to either heart failure or deep vein insufficiency in your legs. Also kidney or liver disease can sometimes cause leg swellingg. Morbid obesity and some medications can contribute or cause leg swelling. Brown discoloration of legs is caused by long standing leg swelling and is called stasis dermatitis.
Venous Insufficiency. Leg swelling and brownish discoloration of the legs could be signs of venous insufficiency. There are many causes of leg swelling and there could be other reasons for brownish discoloration but the two together suggest chronic malfunctioning of the leg veins. See a vein specialist for a full venous evaluation including a venous duplex ultrasound.