It's not often that a new high-quality reference book gets published, but I just got wind of this one today:

  • Pénichon, Sylvie. Twentieth-Century Color Photographs: Identification and Care. Getty Conservation Institute: 2013, 360.

It covers all the possible (and mostly dead) analog colour processes, how to identify them, how to store them, how to preserve them, their history, and so forth. Has useful timelines, lots of hitherto hard to find information, an excellent first chapter on the muddled early days of colour photography in the 19th century, and lots and lots of reproductions and microscope pictures.