A heliochrome, derived from the roots "helios" =
sun and "chroma" = color, (literally sun colors), is a color
, particularly one developed using the incomplete
es from the late 1800s and early 1900s.
In the 1860s, John
discovered that a sheet of blackened silver
exposed to the sun under red glass would turn red in color. Under
blue glass, it turned blue. Other colors resulted in a muddy purple