Hello there Blenderartists! I wanted to post about this odd texture that I found when trying to port a model from a videogame over. It’s annotated with “Masks” which gives the impression of a simple masking stencil for texture painting? But it’s full of green, peach and black rather than the usual white and black. Does anyone know what the purpose of this texture is? Or is it just a very odd stencil mask?
Thanks in advance! 
Going by the areas that are painted, i would guess its something to do with subsurface scattering
It could be channel-packed: as in has 3 black and white maps in one RGB image.
The reason devs do that is conservation of video memory. It is more efficient to pack non-color data like specularity and roughness into channels of the same texture, than to use a separate grayscale image (which will be treated as RGB by video adapter anyway) for each
As @stray said, it is a channel-packed image where different Masks are used on the character for different effects…A mask in character material usually maps certain shaders Like AO or Specular, Shinny, or any number of maps for greyscale data.
In this case, and depending on the game in question, this looks like it might be for dirt or some other effect, possibly blood splatter…hard to tell without seeing the other set of maps that go with this…
The best thing to do is to see what other maps are designated take this one into your material editor and use a split color, then Shift+Ctrl to view directly each of the RGB Channels, Check the Alpha also as sometimes roughness or even AO can be packed into those channels…
Once you have an idea of its possible use, use it as a factor for a Mix color node combining it with the Diffuse and possibly another color map…as an overlay.
I am curious as to what it is, seeing that green covering unusual areas of the face and rather sharp edges is a bit strange…they are usually made with a noise of some type to breach up the edges…
I just took a look at your upload and Red looks like an SSS mask for the ears, nose, and cheek areas…
Green looks like either a Blood or Wet map ( cold be dirt also)…
Blue is a Lip Mask for possible different Makeup or also could be wetness, but I am again curious as there are small areas on the lower eyes and the tips of the ears that would add to those areas… Poke and Hope on Blue…
Something else to consider is that sometimes a “color map” is actually just: multiple parallel channels of data, per-pixel. They don’t actually correspond to “pixel colors.” It’s just a convenient file-format. “What the data actually means” is up to the game-programmer.
