In the Catholic Church, the clerical dress (cassock) of cardinals is scarlet red in color. Are there any other catholic prelates who may don red cassocks?
The Archbishops of certain sees are entitled to wear red ex officio, whether or not they are cardinals.
The Patriarch of Venice has this right, as do the occupants of sees holding legatus natus (born legates, or legates as of right) status. Archbishops of these sees have the right to wear red. These include Salzburg, Udine, Cologne and Poznan.
Prior to the Reformation, Canterbury was a legatus natus see.