This Humayun statue represents Humayun’s royal attire and planetary affiliation for Saturday, Saturn – Black attire. It was the day assigned for reception for literary and religious persons. 
Humayun organized his administration based on his knowledge of the cosmos with ministries of Atashi (fire), Hawa’i (air), and Abi (water). The Ministry of Water would thus be responsible for irrigation while the Ministry of Fire would oversee the army’s artillery and weapons.
Many schools of Hindu astrology consider each planet to be associated with a specific influence; and those specific planets govern specific days of the week. Humayun followed this system and when organizing his daily schedule, he would only attend to subjects related to that day’s particular planet—for instance, he would administer justice on Tuesdays, the day governed by the red planet Mars.