Saw this on the badastronomy.com bbs:

Me and Mars Results - Tonight!
"Then it was Dr. Steve Squyres's turn to talk about the Mars Exploration Rovers, Spirit and Opportunity. He is a superb speaker and gave a very exciting, very fun talk. He is dynamic, and strolled around the front of the stage with his wireless microphone while pointing at the slides on screen. He included bits of humor, including the animation of the rover spinning the RAT into a rock and the rover doing the spinning.
...Then he showed the pictures, many of which have been shown. He started with Gusev crater. They went there because they think it might have been a lake bed at one time, from the surface features from above. He showed the tracks and moving around and looking at rocks, like the Adirondack. He said that is probably a bluish rock with dust on it - yes, that one is bluish. They used the RAT on it and determined it is basalt - lava rock. They're looking for hematite, because hematite is often formed by water.
Next came Opportunity. He has a graphic showing the landing profile for Opportunity, and how it falls, bounces in a nice curving path to score a hole in one on the crater at Meridiani Planum, a site selected for possible hematite from orbiter images. He says he doesn't play golf, but now might take it up - ha ha. The landing site is called Eagle, named after the Apollo 11 lander, but also because an Eagle is a good shot in golf.
The first images showed the amazing outcrop that looks so huge, and is actually about a foot or so across from top to bottom. He talked about the various poking around and investigating. He mentioned the airbag bounce marks and showed pictures where you can make out seam lines. The surface was rough and pebbly, but the bounce marks were smooth, so they wondered if the rocks were crushed or just pushed into the surface - tests showed the latter.
He says the blueberries are hematite. They put the spectrometer on the blueberry bowl (a depression with a collection of the blueberries in it), and the readings showed hematite. He feels they are concretions, based on the shape, and on features like the double and triple berries merging together, and the material being hematite.
He also talked about the other surrounding rocks, and the jarosite, and the spikes on the spectrometer for sulfur. The high sulfur content speaks of water. And also the presence and concentrations of bromine, which are typical of formations from evaporites - rocks formed from evaporating water. Plus there are the depressions that look like blanks for crystals, which are consistent with gypsum, a sulfur type crystal that can form and wear a hole in rocks and then dissolve away later.
They took questions and answers, and nobody asked anything stupid. One person did ask about the spirals, and Squyres said they are at the low end of the resolution so they are hard to make out well, but they have seen several, and only on spots they have RATed, so he thinks they are an artifact of the RAT. They are looking at some experiments to confirm the hypothesis.
He was also asked about how the soil early on looked possibly wet or muddy, and he mentioned that we have to be careful about appearances from things affected by the landers. For instance, the airbags use a burning process to generate the gas, which puts out a number of products including a couple of liters of water. Thus the need to be careful about looking at things close to the landers."
http://badastronomy.com/phpBB/viewtopic.php?t=12076&sid=13ebbcfb09b774637c3224d80323d783

Interesting that Squyres refers to Adirondack as being bluish subsurface.

Here are some other attempts at color representations of Adirondack after the RAT:

From Michael Lyle

From Woodlock

These are probably more accurate than the prior ones I posted since the colors of the ground and the surrounding rocks are closer to the those in the images of the NASA released images.

Bob Clark

cf.:

Space Sciences
Blue subsurface on Adirondack rock?
Posted by Robert Clark on 2/18/2004 7:14:58 PM
http://habitablezone.com/space/messages/314637.html