A coloring agent is a substance used to add color to an object or material. DYE, with three letters, is a type of coloring agent that is applied in a liquid form and bonds with the material it is being applied to. A dyer, with four letters, is a person who specializes in using dyes to color fabrics and other materials. Smalt, with five letters, is a type of blue pigment made from cobalt glass. STAIN, with five letters, is a type of coloring agent that is applied in a dry form and penetrates the material it is being applied to. TONER, with five letters, is a type of coloring agent used in printing and photocopying to create images on paper.