To lower wind resistance and maximise damage when they commit suicide by running head first into walls to see infrablack.

Quote Originally Posted by Good Omens
The technical term for it is infrablack. It can be seen quite easily under experimental conditions. To perform the experiment simply select a healthy brick wall with a good runup, and, lowering your head, charge. The color that flashes in bursts behind your eyes, behind the pain, just before you die, is infrablack.