Blue corn flour is ground from blue flint corn (aka Indian corn.)
The flour has a greyish-blue colour, turning more blue when cooked.
It generally has a coarse texture, and therefore consequently gives a denser finished food product than white or yellow corn flour.
It is used for making atole, chaqueque, corn chips, nixtamal, piki bread, and tortillas.
Harina Azul (aka Harinilla) is a Mexican blue corn flour made from blue corn that has first been soaked in water with lime (the mineral) in it.
It us used for making tortillas from.
Harina para atole
Harina para atole is made from blue corn that has been toasted. It is used for making Atole from.
For Harina Azul, you can substitute masa harina for a similar taste, though the colour and texture will be different.
Blue corn flour was the corn flour preferred by the Hopis, the Navajos and the Pueblo Indians.