To answer my only question, as expected, dirty faces are created under the "Character Gen Parts" tab when editing the NPC from the Actor list in the "Object Window". However under textures the dirty face was likely created by using more than the dirt options at the bottom of textures. To remove all dirt from a face right click on each texture in the list (except warpaints and tatoos, unless you are trying to get rid of these also, untested) and anywhere (except skin tone) there is a color except ColorAverage, R 255, G 255, B 255, change the color to ColorAverage under "Face Tinting Color." You should also check "Face Complexion" if the face is to rough. Yor And don't forget to export after saving the NPC, by highlighting the NPC in the "Object Window" list and hit Ctrl-F4, or they will be grey faced in game.