Explanation:

One of the brightest craters on the Moon is the 40 km wide Aristarchus in northern Oceanus Procellarum. Nearby is the largest lunar rille, Schroeter's Valley. Both of these cut into the largest and strangest, but historically often overlooked mare island, the Aristarchus Plateau. Or the name I prefer, Wood's Spot, named after early 20th century astronomer R.W. Wood who discovered that the plateau is anomalously bright in the ultraviolet. In the visible the plateau is one of the lunar areas that sometimes seems faintly colored - once I saw it as a delicate mustardy green. Compare this oblique Apollo view with Tom Williamson's color webcam image. Note the dome in the bottom left-center of the image.

Related Links:
Aristarchus Region
Volcanic History of Oceanus Procellarum