This is too complex.Originally Posted by Nyarochrome100D
What you want is a high contrast mask for the image (color) you want to increase in saturation. Methods are shown in the Kodak Dye Transfer publications, but are now out of print.
Another method is to bleach, but not fix a print, then redevelop, bleach, redevelop and bleach until you achieve the color saturation / contrast - that you want.
The first method above can target a single color, but the second enhances overall contrast and saturation.
There are many ways to get at this problem. Simply using the high saturation films and print materials will often satisfy your needs.