For my 2d game I added lighting by simply rendering a circle-gradiant-textured quad over the light source and making is transparent. It works well, but since my game takes place in outer space, it looks kind of lame since the transparent color shows up on the black background(you guessed it, space!). How can I make it so the blending only affects colors greater than 0? (black is 0.0, 0.0, 0.0, obviously) I’ve thought maybe experimented with various glBlendFunc parematers would achieve thes results, but i havent found one that works.

You could try alpha testing with blending. This is just an idea. Wether it works or gives you the result you want, i dunno.