Hand Coloring

Hand-coloring refers to any method of manually adding colour to a black-and-white photograph, generally either to heighten the realism of the photograph or for artistic purposes. Hand-coloring is also known as hand painting or overpainting.
You can use, watercolors, oils, crayons or pastels, and other paints or dyes on top of your image.
You can apply the above using brushes, fingers, cotton swabs or airbrushes. Hand colored photographs were most popular in the mid- to late-19th century before the invention of color photography and some firms specialized in producing hand colored photographs.

these images would have been done in a dark room in black and white then the color would have been added after by hand.