Context: 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).

Question: What color is the hat?
Answer: white

Question: How are Cardinal deacons recognized at Masses?
Answer: Unanswerable

Question: How are Cardinal deacons recognized at Ecumenical Meetings?
Answer: Unanswerable

Question: How are Cardinal deacons recognized at quarterly Urbi et Orbi papal blessings?
Answer: Unanswerable

Question: What do nuns wear in addition to the simple white mitre?
Answer: Unanswerable