The term 'dark brown pigment' can refer to three different substances: UMBER (5 letters), SEPIA (5 letters), and Burntumber (10 letters). UMBER is a natural earth pigment composed of clay and iron oxide, which gives it its dark brown color. SEPIA is a reddish-brown color derived from the ink of cuttlefish, and is often used in art and photography. Burntumber is a synthetic pigment created by burning raw UMBER, which produces a darker shade of brown.