skybox unity code example

Example: unity skybox black

I figured this would be quite simple - i simply want to render black anything that is not part of my geometry - my lightmap fades to black, but then everything rendered outside of the geometry is gray.

I even tried createing a 'black' skybox...but still, everything is gray. I figured there would be a very simple way to change the render color for the background...maybe i'm just missing it?

Thanks!