© Denzil Green
Blue Corn is a variety of flint corn that is blue.
It is also a variety that is harder to grow. It produces a lower yield than other types of corn, and its stalks tend to just fall over in the fields. In compensation, it has more of a “fuller” corn flavour than white or yellow corn. The flavour is sometimes described as sweet and nutty. These factors lead to its being more expensive than other types of corn.
It is very popular for the flour that can be made from it for tortilla chips. The kernels can also be used for posole.
Turns a light purple when cooked.
Blue Corn has 20 to 30 % more protein that other corns.  
The protein in it is also considered to be a more “complete” protein than in other corns, owing to the higher levels of lysine in it. [Ed: note “more complete”, not “complete”, as some sale sites advertise. 
 “Scientists in Mexico… found that the blue tortillas had 20% more protein than white.” — “Blue Tortillas May Help Dieters And Diabetics”. ScienceDaily. 1 August 2007. Retrieved October 2010 from http://www.sciencedaily.com/releases/2007/07/070730092559.htm.
 “Studies at Colorado State University indicate that the protein content of commercial blue corn is consistantly 30% higher than dent corns in adjacent fields (Johnson and Croissant 1990). ” –Johnson, Duane L., and Mitra N. Jha. Blue Corn. In: J. Janick and J.E. Simon (eds.), New crops. Wiley, New York. 1993. pp 228-230.
 “In an evaluation of five New Mexico blue corn varieties by the New Mexico Cooperative Extension Service in 1990, all were found to be higher in lysine (averages of 2.3 mg/g of dry kernel) than two commercial varieties of yellow (1.4 mg/g) and white (1.6 mg/g) dent corns used for making tortillas. Thus, like opaque-2 corn varieties, blue corns are a more complete protein source than either white or yellow dent corns.” — Dickerson, George W. Nutritional Analysis of New Mexico Blue Corn and Dent Corn Kernels. Cooperative Extension Service, College of Agriculture and Home Economics. New Mexico State University. Publication H-233. 2003.