Simple three-layer carpaint shader. I tested the .igm with Blendigo 1.1.5 and it works fine. You can vary the rgb values for different looks. (sorry for the time stamp on the preview. Forgot to turn it off.)
Bad format ! There's a material named "Ground" in the last place? What ground? Why the other materials are there then? =)
Have fixed the igm file, and rendered a new preview image.