Today's Image of Mars shows some spectacularly colored gullies in a relatively fresh crater on Mars near Argyre Basin. The crater is in such pristine condition that scientists believe it was formed within the last million years or so.
You can see in this image that the gullies and their deposits have many different colors. This is because the relatively recent impact exposed many different rock types and the gullies are still active, so they have yet to be covered by windblown deposits.
Clicking on this image will take you to the original high resolution image from HiRISE. I highly recommend checking it out because it's pretty amazing. [See the HiRISE caption for the image].