Along the ice cap margin, you can see oulet glaciers that drain the main ice body. Most of the outlet glaciers show up as dark. This is because in the ablation zone all of the previous winter's snow has melted by the end of summer, and bare ice shows up as dark. You can also see medial and lateral moraines on some of the outlet glaciers. The red areas in this false color image are those areas covered with vegetation.
Dark areas are lava fields and water.
The large dark area between the ice cap and the coast is the sandur plain of Skei araj kull, one of the largest outlet glaciers that drain Vatnaj kull. Some areas along the coast have a bluish tint. This is meltwater carrying silt and discharging into the north Atlantic.