Actiually, if I'm interpreting the BBC item about it correctly, the moon that is parti-colored is actually closer to Saturn than the E-ring is, but there IS a (different) moon that orbits within the E-ring (i.e., the inner edge of E is closer than this moon; the outer edge is farther). That moon - Iapetus/Japetus, IIRC - disturbs the particles of the E-ring, causing them to spiral in toward Saturn, and the parti-colored moon - Phoebe, IIRC (I may have swapped them) - runs into them 'like bugs on a windshield' to paraquote the Beeb.