There could be multiple layers on DriverCloth shader, where Diffuse texture is premultiplied with DiffuseColor1 given as rgb in a material file. Additionally (as in most of shaders I've explored to the moment), the specular map is usually a per-channel mask texture, where .R is usually specular glossiness, and .G is often a colorization mask. Thus, for example, a DiffuseColor2 could be masked by SpecularMap green channel, so you could have multiple color clothes dress. The second diffuse texture is (usually grayscale) a premultiply or overlay details for fabric texture simulation (that's where my shader gives dark effect on pants - if I disable fabric detalization, pants are drawn with correct blue color; same on hat). Additionally, a normal map #2 can be used as displacement map to simulate small bumps or fabric texture.
So, in general, the correct color is usually "Diffuse1Color" premultiplied by DiffuseTexture1 and mixed with Diffuse2Color masked by Specmap.Green;
I'll port DriverHair and DriverEye today to see whether these works the same way.
To say, most of info is generally in "materialdescriptor" folder as you've mentioned earlier. Some shaders specify a per-vertex color masking info, so per-vertex color component is NOT the color of mesh, it's a per-vertex effects masking. E.g. wetness areas are masked via vertices color channel (R on some shaders, G on another). Quite comprehensive to deal with as I see...
