Yeah I thought of this too this night.
I ran into some materials informations coming from a UDK file it seems, called Material Instance Constant. Unfortunately, opening it with Notepad just told me the name of the Diffuse and Normal files, nothing useful. And I don't have Unreal Engine installed, nor I know how to use it.
By searching for this Material Instance Constant, I learned that it's used to modify textures on an instance basis with some parameters. So they probably could use this kind of material to modify the color on the fly with values instead of textures ( Which would explain why there is no other texture used ) ?
So I considered the left part to be some kind of lightmap as >>498090
said, AO and all, which are pretty much details so they are not important for now, I will figure this out later.
The right part seems to be a mask then, and the channels could be used to define 3 different colors. But some things doesn't fit, like the armband on the right which is on green-channel but should have the same color than those on the red-channel, or some parts of the pants which should be on the blue channel but are not...
Oh, this thing is giving me a headache already. I think I will just modify the diffuse texture directly by hand and whatever. Thought it would take me more time to do this than understand how it is working, but I guess not.
If anyone have some UE experience and can tell me what's going on, I will gladly take it. But in the meantime I will just get around for now.
Thanks for trying to help guys, I appreciate.>Mfw absolutely all the characters are done like this and I will have to recolor all textures I want to use