Hand Tinting a Photograph with Photoshop
http://www.graphic-design.com/Photoshop/hand_coloring/

Shelbourne, Tim
Photoshop Tips and Tricks
2006

Abstract:

Before the age of color film, when black-and-white photography was the only option, it was common practice for photographers to tint a black-and-white image with colored dyes to mimic real-life colors. Although we now have all the advantages of stunning color photography, we can still use Photoshop to replicate this technique, and add great charm to black-and-white images.