Galero was a broad-brimmed hat with a shallow crown. The members of the catholic church wore it till the Papal Decree of 1969. The red Galero was reserved for the highest-ranked cardinals and was ceremonially presented to them by the Pope. Lower-ranked clergies wore green and violet-colored hats.
After the Papal decree, Galeroes were not worn anymore and were replaced by Zucchetto and Biretta; however, there is a custom of suspending Galeroes over the cardinals’ tomb when they expire; therefore, many Cardinals still acquire the Galero privately from the Pope.
Initially, Pope Innocent IV used the Galero to distinguish his favorite cardinals in a procession, but later on, it became a tradition.