Today's Image of Mars comes from HIRISE and shows distinct sedimentary layers on the floor of Ritchey Crater. These layered deposits help to provide insight about the past climate on Mars and the periods of change The Red Planet went through.
The blues and greens in the image are indicative of dry periods where the minerals were not altered by the presence of water. Examples of minerals that would fall into this category are olivine and pyroxene. The warmer colors, like the oranges and yellows, are minerals like sulfates and clays that were formed in the presence of water.
Clicking on this image will take you to the original high resolution image from HiRISE. [See their caption for this image]