Cardinal Buoys can be either Quick Flashing or Very Quick Flashing so that they can be distinguished when used in multiples - perhaps protecting a long sand bank for example.
Colour described on charts as:- BYB- for Black over Yellow over Black.
Memory Aids:-
The two arrows point in the opposite direction to the West Cardinal buoy.
The arrows always point to the black sections - in this case the upper and lower sections
East is at “Three o’clock” on the Compass - so three flashes.