How do I modify this colored Mesh in Illustrator?

I have this nifty glowing ring in an EPS file. I am trying to figure out how to use Illustrator to have the same blue ring with a white background.

I'm having difficulty understanding where the black background comes from. I know that the layout of the file is a number of overlapping circles, then a single mesh that results in the final output. When the Mesh is hidden:

On that Mesh, I think the blue color is controlled through the "Recolor Artwork" dialog

Knowing now how the effect is constructed, how would I go about having the same blue effect with a white background?