Craters can be very useful in exposing features that were once hidden beneath the surface. Here, the edge of a crater wall exposes a cross-section of enhanced color bedrock in Syrtis Major, a relatively dust-free region of Mars.
The diverse colors represent rocks of differing compositions and types. There are a few large clasts, or chunks of rocks, indicating that some of the underlying rock was broken up by some past high-energy event. [More at link]