The Collaborative International Dictionary
Heliochromy
Heliochromy \He"li*o*chro`my\ (h[=e]"l[i^]*[-o]*kr[=o]`m[y^] or h[=e]`l[i^]*[o^]k"r[-o]`m[y^]), n. The art of producing photographs in color.
Wiktionary
heliochromy
n. (context dated English) The art of producing colour photographs.