The sand on Mars is from basalt, which is a darkish gray color. The red comes from much smaller dust particles which settle everywhere.

But what are those weird tendril thingies?

In the Martian winter, carbon dioxide freezes out of the air. In the summer, that CO2 sublimates; that is, turns directly from a solid to a gas. When that happens the sand gets disturbed, and falls down the slopes in little channels, which spreads out when it hits the bottom. But this disturbs the red dust, too, which flows with the sand. When it's all done, you get those feathery tendrils.