Quote from the COLREG topic :)
IALA buoyage system.
At sea are 2 types of buoyage systems known, IALA A and IALA B. IALA B is used in America, Japan and the Philippines, IALA A is used in the rest of the world.
(http://i40.tinypic.com/wgrfy9.gif)
The only difference between IALA A and IALA B are the lateral buoys. At IALA A you have the red buoys on your portside, at IALA B you have the red buoys on your starboard side when you are following the buoy direction. The buoy direction is from sea towards the harbor, at sea the buoy direction is shown by a symbol in the chart.
(http://i44.tinypic.com/2qdxzys.gif)
Chart symbol that indicates the direction of the buoys
There are 5 types of navigation buoys:
• Lateral buoys. Red or green, they indicate the border of the fairway and indicates the direction
(http://i39.tinypic.com/1429b1i.gif) (http://i40.tinypic.com/2dsnu3c.gif)
•Cardinal buoys. Yellow and black, they indicate the safe side of the danger (e.g a wreck or a sandbank). Looks pretty hard to remember, but actually it's pretty easy if you look at the top marks. The north buoy and south buoy point towards the north and south (obvious), the topmark of a westbuoy has the shape of a wineglass. When you know the other 3 the 4th, the east buoy, is easy. ;)
(http://i41.tinypic.com/691hlu.gif)
• Isolated danger. Black and red, they indicate the position of isolated danger, contrary to cardinal buoys which indicate a direction away from the danger.
(http://i40.tinypic.com/20adl5x.gif)
• Safe water. Red and white, indicates safe water. Also known as a mid fairway buoy.
(http://i41.tinypic.com/10fyy6s.gif)
• Special buoys. Yellow, indicates pipelines, special areas etc. etc.
(http://i42.tinypic.com/1zfljpt.gif)