The human brain has several parts, and each has a distinct coloration. The surface of the cortex is often referred to as gray matter to distinguish it from the myelin-sheathed nerves underneath it, which are a much brighter white.
The basal ganglia of the neurons contain a special pigment, called neuromelanin, that stains them black. These areas are called substantia nigra, or "black matter," in Latin. The brain is also heavily vascularized with elaborate networks of blood vessels feeding every part of it. The blood in these vessels imparts a reddish or pink hue to most of the living brain's tissues.