Muhammad I of Granada, the founder the last Spanish Muslim kingdom, was also known by the name "Ibn al-Ahmar" ("son of al-Ahmar") The dynasty he founded, the Nasrid dynasty, was also known as "Banu al-Ahmar" ("children of al-Ahmar").
It seems that ''ahmar'' simply means "red" in Arabic. How did Muhammad I and the dynasty come to be associated with these names?