The background color I believe is under the camera attributes (panel menu: view > select camera > attribute editor) under environment color or something similar. I believe the background color should not be included in the alpha channel, so if you open up a file in a format that supports the alpha channel, the background should be interpreted as transparent (regardless of what color you set it as). Hope that helps. Brilliant! Thanks Stwert, another mystery cleared up. I'm getting there, albeit very sloooowly.