Most of the world follows IALA A.
Pretty much only the Americas, Japan, Filipines and South Korea choose to be different (IALA B).
http://www.nauticalissues.com/en/iala.html
gives more details.
However, the shape of the port and starboard buoys is the same in both regions (cans/squares to port, cones/triangles to starboard).
Cardinal signage is the same in both regions, I think.