The color_map is the same as an image_map, just differently named. 

And as a side note, Vestmann is correct about the VSSProp.  Do not attempt to add any texture maps to the prop itself.  The script is written in such a way that it will overwrite and incorporate and shader nodes connect to the posersurface node.  So, if your original model has 1 texture map connected to Diffuse_color, when you synchronize VSS, the model's original connection will be overwritten and the texture map will be assimilated into the VSS shader pipeline.

Edit: I agree with Vestmann, the VSSProp manual should be rewritten to reflect the current node arrangement, the newer albino skin VSS, and demo how to construct a VSSProp for props and hair.