This view is the closest color view of Umbriel (the closest view is colorized based on this image). Thank to spacecraft motion, the phase angle is growing, and the heavily cratered, dark moon can be seen to have several bright spots, most notably the extremely bright crater rim near the top of the disk, Wunda.
This is Voyager's best view of Umbriel and its cratered surface. It appears that their is a degraded tectonic feature near the bottom of the terminator. Wunda sits prominently at the top of the disk, and another crater, Skynd, on the upper terminator lacks a bright rim but has a bright central peak.
This view of Wunda, produced using the last two images shown here and reprojected to be seen as if viewed from above, shows the doughnut-like shape (with a tiny segment missing pointing diagonally down and left).
Processed Images Copyright Ted Stryk, Raw Data Courtesy NASA/JPL