Toronto. The most popular modern day photographic techniques rely on the tri-colour vision of humans. Using only three colours in various strengths the entire visible spectrum can be seen by the human eye. There were are basic techniques, so called additive (RGB) processes and subtractive (YMCK) processes.
The first was used mainly in transparencies for about 35 years since by its very nature the additive processes reduce the light transmission rendering the method extremely slow. After the mid 1930s the subtractive processes came to the fore and offered prints and faster speed transparencies.
The Frenchman,Ducos, predicted and often patented the colour options well ahead of any capability to commercially create them. Louis Ducos du Hauron lived a long life from late 1837 to the summer of 1920. One again, I am indebted to Brian Coe who wrote on photographic history while the curator of the Kodak Museum in England. His theme in his 1978 soft cover book is Colour Photography.