Crayons are colouring materials.They are employed in paper ,board walls etc.Dpending on the medium in which you want to use You can use base materail such as waxes, plaster of paris, etc with inorganic pigments of various colours.
I am a post graduate in chemistry. Have got more than 40 years of experience in the manufacture of soaps ,plasic products, rubber, lubricants etc. I am retired and interested in sharing my knowledge if it is of some use to other free. I spend about two to three hours in the net to learn about the new developments. If any body is interested they can contact me