There. Grey-faces are fixed for at least the NPC’s I’ve created so far. These two barkeepers now look a whole lot better. They’re still giving me the scary stare though. We’ll deal with that later.
The fix is simple. You just need to select your NPC’s in the Object window in the Creation Kit and press Ctrl and F4. This generates their FaceGen Data which is then found in textures/character/FaceGen Data/FaceTint/[your mod name]. Since I’m working with an .esm, I needed to open the .esm-file in the CK and do it. It works similarly with .esp’s. The only problem I see is that it generates quite large files and it will swell my file-size even more. Sigh.