Colour described on charts as:- YBY - for Yellow over Black over Yellow.
By Day.
By Night.
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.
Memory Aids:-
As far as the arrows are concerned, “west” is like a “waist” - but some people also say that it is like a “W” on its side.
The arrows always point to the black sections - in this case the central section
West is at “Nine o’clock” on the Compass - so nine flashes.