Wikipedia
Blue corn (also known as Hopi maize) is a variety of flint maize grown in Mexico and the Southwestern United States, particularly in the states of Arizona and New Mexico. It is one of the main types of corn used for the traditional Southern and Central Mexican food known as tlacoyo.
It was originally developed by the Hopi, and remains an essential part of Hopi dishes like piki bread. Blue corn meal is a corn meal that is ground from whole blue corn and has a sweet flavor. It is also a staple of New Mexican cuisine.
In addition to its sharply different color, blue corn has several nutritional advantages over standard yellow or white corn varieties. It contains 20 percent more protein and has a lower glycemic index than white corn. When used to make tortillas, blue corn produces a sweeter, nuttier taste than yellow or white corn, and is a more complete protein source. A certain technique is used to grind the blue maize to make it release niacin.