The color imager on Mars Odyssey should have about the same resolution as the Viking orbiter, about 20 meters/pixel.

A question about some features on Mars is whether some color differences are real or are only apparent in comparison to surrounding terrain.

White Rock for example has been claimed to not really be white but only lighter than the surrounding area. Will the color imager be able to determine if it really is white?

Another area where the interpretation of its color has been controversial is the Syrtis Major region. It has long been known to present an apparent bluish tint that appears to change seasonally. William Sinton made some spectrographic observations of the area in the 50's that appeared to show it's spectrum matched that of complex organic molecules. This and the seasonal changes led Sinton to originally propose the spectra were due to life. Will Mars Odyssey be able to determine if Syrtis Major really does become blue seasonally?
Some of the bands Sinton observed have been explained as actualy due to HDO in Earth's atmosphere. However, the bands at 3.4 microns which are frequently seen in complex hydrocarbons have not been definitively explained. Will the THEMIS infrared imager on Mars Odyssey finally be able to resolve the mystery of the "Sinton bands"?

The history of the Sinton bands is told in the second chapter of Barry DiGregorio's book, _Mars: the Living Planet_,
http://www.amazon.com/exec/obidos/ASIN/1883319587/marsbugstheelect

References on the Sinton bands:

Home Page for IRTF Mars Image Gallery
Sinton bands in February 1995 IRTF images
http://marswatch.astro.cornell.edu/irtf.html

3-4m mm IMAGING SPECTROSCOPY OF MARS.
http://www.lpi.usra.edu/meetings/LPSC98/pdf/1658.pdf

It's also discussed in the dissertation of David Klassen:

Infrared Imaging Spectroscopy of Martian Volatiles
by David R. Klassen
http://elvis.rowan.edu/~klassen/papers/dissertation/chapter1.htm

Bell et.al. have also proposed the aluminum mineral diaspore
for the origin of the "Sinton bands":

SPECTROSCOPIC EVIDENCE FOR DIASPORE (a-AlOOH) ON MARS.
http://www.lpi.usra.edu/meetings/lpsc2000/pdf/1227.pdf

Bob Clark