In accordance with the wuxing(five phase) philosophy, which linked certain colors with particular directions, elements, and seasons, the emperor and his entourage wore blue robes when paying sacrifice at the Altar of Heaven or the Hall of Annual Prayers, red at the Altar of the Sun, light blue for sacrifices to the moon, and yellow for rituals at the Altar of Earth. The blue color of this robe associates it with the imperial sacrifices at the Altar of Heaven, ceremonies intended to ensure rainfall for the Chinese agrarians.