Given the question: I know that the answer to the question "What do the subjects do?" is in "When not celebrating Mass but still serving a liturgical function, such as the semiannual Urbi et Orbi papal blessing, some Papal Masses and some events at Ecumenical Councils, cardinal deacons can be recognized by the dalmatics they would don with the simple white mitre (so called mitra simplex).". Can you tell me what it is?
The answer is:
they would don with the simple white mitre