One of the ways color was added to black and white silver prints was through hand coloring. A whole industry revolved around photo dyes or oils being added to portraits, scenes, and other photographs. It is now possible to replicate hand coloring digitally.
Color photography has been around for a long time, but there were no easy developing processes available for a personal darkroom until the 1940s when Ektachrome was marketed by Kodak. I began using the E-6 process to develop positive transparencies (slides) in the 1980s and also did printing from both negatives and positives. Around that same time, the photo paper and process that was known as Cibachrome and which could be processed in a small darkroom became available. After Ilford purchased the Ciba company, the paper was called Ilfochrome. It was a beautiful paper producing glossy, sharp images with deep vibrant color. I had an exhibition of Cibachrome prints at the Kruk Gallery, University of Wisconsin-Superior in 1987.