33 CFR 5.42: Auxiliary ensign.

(a) Description. The field of the Auxiliary ensign is medium blue (Coast Guard blue) with a broad diagonal white slash upon which a matching blue Coast Guard Auxiliary emblem is centered. The white slash must be at a 70 degree angle, rising away from the hoist.

(b) Display. The Auxiliary ensign may be displayed by any member of the Auxiliary on a vessel, aircraft, radio station, building, or other location at any time, under such conditions as the Commandant may direct.