Light bounces around the Saturn system in strange ways. The Sun is the only light source, but incoming sunlight strikes Saturn and its rings and its moons and bounces off to illuminate areas of Saturn and its rings and its moons that would otherwise be dark. In particular, Saturnshine and ringshine have been useful to Cassini's efforts to image areas of moons that would otherwise have been in the dark.
Here's a nice color image captured during Cassini's prime mission to Saturn that illustrates how much ringshine was bouncing around the Saturn system then. Anyone floating among Saturn's cloud tops during the night on Saturn would be dazzled by the arc of brilliant rings overhead, and would surely have enough light to see by. (This is one of many spectacular color composites of Cassini images produced by Gordan Ugarkovic.)
If you couldn't follow that, don't worry. Just look at the photo and allow yourself to be amazed. Sometimes I find myself thinking too much and have to exert effort to step back and just be amazed by what we're seeing.
Here's one last amazing pic, on the topic of Saturnshine and moon shadows.