46 CFR § 153.953
Signals during cargo transfer
April 15, 2021
The master shall ensure that:
(a) The tankship displays a red flag in the day and a red light at night when transferring cargo while fast to a dock;
(b) The tankship displays a red flag when transferring cargo while at anchor; and
(c) The red flag or the red light is visible from all sides of the tankship.