What color of flag indicates a vessel is engaged in diving operations and is restricted in maneuverability?

There are 2 "Divers Down" flags

A white, diagonal bar on a red background is a common sight in North America but is not commonly seen elsewhere. Its meaning is also less precise.

and the

The A flag or Alfa (alpha) flag which is a half white and half blue flag has a clear international meaning meaning: "I have a diver down; keep well clear at slow speed "