Tetrachromacy is the ability to see many more colours than normal people.
Tetrachromats can be only women as the genetic information for the 4th colour receptor can be located on one of the X chromosomes. This "mutation" is very rare and enables the person to view and distinguish around 100 million colours.
Tetrachromats can at the same time wear contact lenses or even have an astigmatism. This does not influence their capability to see many colours.
Concetta Antico is one of the most famous Tetrachromats as she uses her unique ability to express herself in art.
Visit http://concettaantico.com/ to learn more about her work