Download a theme creator such as myTheme Creator or SE Theme Creator, open an existing theme or create your own, and you should see an option that enables you to set the illumination color to whichever color you want (though the w580i only supports certain colors, so it will choose the color closest to the one you set if it doesn't support that exact color).

Save the theme as a .thm file and upload it to your phone and when you set it, the illumination color should change with the theme.