The brighter parts of the Keck image shows where there is less water ice. The Voyager image is of a slightly different face than the Keck image; the non-water ice spot that shows up so clearly in the Keck image is the paleish reddish yellowish terrain in the bottom left quadrant of the Voyager image. The composition of that material has been a mystery since the time of Voyager.

Keck image: Mike Brown; Voyager image: NASA / JPL