We know that Prokudin-Gorskii intended his photographic images to be viewed in color because he developed an ingenious photographic technique in order for these images to be captured in black and white on glass plate negatives, using red, green and blue filters. He then presented these images in color in slide lectures using a light-projection system [right] involving the same three filters.




source.. http://www.loc.gov/exhibits/empire/making.html