In Region A it is a starboard hand buoy, in Region B it is a port hand buoy. These are lateral marks and in some areas the shape of the buoy cannot be relied upon.
Since this is a Green Lighted Buoy sighted while approaching a harbour,this is a Lateral port hand side mark, IALA region B. To keep this buoy on your port side while travelling upstream.
A port or starboard buoy depending on what region you are in
Blue
Keep the buoy on your port (left) side.
They pass Port To Port side
Blue
Blue
Blue
Blue
Keep buoy to right going upstream.
I think you should----Keep the buoy on your port (left) side.