Mars may look red from here on Earth, but up close, the surface of the "Red Planet" is actually a variety of colors. In fact, many of them aren't very red-looking at all.
Case in point: the dunes in Mars' northernmost latitudes, like the ones pictured here. But wait a minute, you may be thinking. Those dunes look pretty red to me, or at least a little pinkish. And you'd be right — if what you were describing was in fact the Martian surface. But it isn't. [Hi-res image available here]
What are these black splotches on the surface of Mars? Those black splotches are the surface of Mars. The dunes only appear pink because they are covered in frozen carbon dioxide. NASA HiRISE scientist Cindy Hansen explains: