Color-Key, produced by 3M, is a method of making pre-press approximations of
3 or 4 color separations from negatives to be used for making printing
plates. As I never used it, haven't kept track, but don't recall seeing
anything about it recently. You might want to get on one of the printing
maillists, or possibly someone reading this can enlighten all of us about
its status.
Sil Horwitz, FPSA
Technical Editor, PSA Journal
silh@iag.net