Abstract: The free bases of various amino dyestuffs, such as the amino derivatives of triarylmethane and xanthene dyestuffs form stable solutions with organic halides and a matrix, such as a film-forming binder. Dry films of such compositions are lightly colored; upon exposure to actinic light, the dyestuffs become intensely colored. The combination of dyestuff free base and organic halide is particularly useful in conjunction with photopolymerizable compositions to denote the polymerized portions of a dry film photoresist and to enable the use of thicker films or coatings of liquid photopolymerizable compositions than were previously useful.