 Improved versions appeared in later years.It used the direct bleach-out method of color reproduction first proposed by Louis Ducos du Hauron and Charles Cros in the late 1860s and based on the fact that a substance can only be affected by exposure to light if it absorbs some of that light.Unstable coloring matter is therefore bleached by light of its complementary color, which it strongly absorbs, but little affected by light of its own color, which it mostly transmits or reflects.