The THEMIS camera contains 5 filters. The data from different filters can be combined in multiple ways to create a false color image. These false color images may reveal subtle variations of the surface not easily identified in a single band image. Today's false color images shows an unnamed crater in Acidalia Planitia. The "dark blue" material is likely basaltic sand.
Orbit Number: 19321 Latitude: 42.1856 Longitude: 359.705 Instrument: VIS Captured: 2006-04-23 05:40
http://photojournal.jpl.nasa.gov/catalog/PIA20231