Below is an excerpt from the recently published paper in Science:

Morphology and Composition of the Surface of Mars: Mars Odyssey THEMIS Results
Philip R. Christensen, Joshua L. Bandfield, James F. Bell, III, Noel Gorelick, Victoria E. Hamilton, Anton Ivanov, Bruce M. Jakosky, Hugh H. Kieffer, Melissa D. Lane, Michael C. Malin, Timothy McConnochie, Alfred S McEwen, Harry Y. McSween Jr., Greg L. Mehall, Jeffery E. Moersch, Kenneth H. Nealson, James W. Rice Jr., Mark I. Richardson, Steven W. Ruff, Michael D. Smith, Timothy N. Titus, and Michael B. Wyatt
Published online June 5 2003; 10.1126/science.1080885 (Science Express Research Articles )
Abstract

"An approximately true color visible image of the relatively bright enigmatic feature known as 'White Rock' in Pollack crater (8°S,25°E) (Fig. 7) indicates that White Rock is actually quite red, consistent with previous lower-resolution Viking color imaging of this feature (28). Indeed, the actual color and reflectivity of White Rock is comparable to that of typical bright dusty regions on Mars, suggesting that it is either mantled by thin ferric-rich aeolian dust deposits or consists of weathered or coated ferric materials. The overall rugged morphology and cliff-forming nature of the feature suggest a competent, possibly indurated, substrate or deposit, yet there is also clear evidence that some material has been eroded from this feature (29). These observations, combined withknowledge of the color of this feature, may indicate thatWhite Rock is an indurated and weathered sedimentary deposit, perhaps deriving some of its resistance to erosion from cementation by fine-grained ferric oxides. Similar 'white' and apparently indurated material was seen at the Mars Pathfinder landing site (30, 31), and was found to be compositionally similar to the surrounding bright drift deposits."

Fig. 7, which is the image you embedded in your post, is THEMIS V03233002. The authors note that they utilized the VIS 0.650, 0.540, and 0.425 micron bands (in 2x summing mode) to generate the RGB to obtain "approximately true color."