Sorry for late response. Been away from Zone for a bit.
The diffuse overlay is by necdaz91, found on DA.
[https://www.deviantart.com/necdaz91]
I had to search, but it was part of the MorphExpansion 2 set:
[https://www.deviantart.com/necdaz91/art/Foot-Morph-Expansion-2-Gen8-and-Gen8-1-879181983]
(sort of buried by now, but still a free download there via Drive)(as of this post, anyway)
(search for necdaz on Zone for other morphs which predate)
Navigate to the ”Maps” subfolder from the zip. There is the Sole_Blusher.png there, and a tutorial on how to use.
It can be dialed to suit, for both amount and for color. The idea is to use a map in the diffuse overlay channel to create a color highlight on top of existing diffuse map.
Thanks again to everyone, btw, for the input and support.