Here is an outstanding shot from the NASA website:
Io is a colorful place. The closest large moon of Jupiter, Io has the most volcanic activity of any moon in the solar system with its surface being completely buried in volcanic lava every few thousand years. The black and red material corresponds to the most recent volcanic eruptions and is probably no more than a few years old. This image by the automated spacecraft Galileo highlights the side of Io that always faces away from Jupiter. In this image, colors have been adjusted to enhance contrast, but are based on real composite infrared, green and violet-light images.