This image covers most of an impact crater about 6 to 7 kilometers wide. Partway down from the crater rim is a prominent bright layer of bedrock.
The full-resolution color data shows three distinct bedrock colors: yellow, light blue-green, and dark blue (in enhanced infrared colors). (North is down in the cutout, so the crater rim is near the top, which helps my brain to interpret the geometry.) These layers must correspond to different types of rock that were deposited as nearly flat-lying sheets, perhaps a combination of lava flows and sediments.
The relatively blue colors in HiRISE infrared color often correspond to minerals like olivine and pyroxene that are common in lava.
Written by: Alfred McEwen (3 October 2012)
More info and image formats at http://hirise.lpl.arizona.edu/ESP_028693_1535
Image: NASA/JPL/University of Arizona