Well yes the image is a composite of a regular render and ZBuffer combined in photoshop to get desired affect. But the when rendering in ZBuffer the image will have the background color of your Assembly room ort what ever color you have set in your preferences for some reason. Even if you goto the scene settings and pick a color for the backdrop or background it will still use the color from your interface. You can control the color of the mesh by simply changing the color in the texture room for hte model. Hope this helps if not I'll post some more stuff.