Iconography is a tradition in the Orthodox Church, and tradition calls for certain coloring, with meaning attached. In Orthodox Iconography, the Theotokos' inner garment is blue, symbolizing her humanity. Her red covering robe, symbolizes the royal role she accepted and took on, to be the Mother of God, her Son being, our "King and God." (Christ on the other hand, is depicted with a red inner garment, symbolizing His Royal, Kingly nature, and He wears a blue robe, symbolizing the human nature he took on.) Not all iconography is this precisely executed, but this is the traditional practice.