Cuttlefish ink, also known as SEPIA, is a dark brown or black liquid produced by cuttlefish and other cephalopods. OCTOPUS, octopi, squids, and other cephalopods also produce a similar substance called ink, which is often referred to as INKY. Cuttlefish ink is used for a variety of purposes, including writing, drawing, and dyeing fabrics. It is also used in some traditional medicines and as a food coloring agent.