These are called preferred channel markers. Which means you can pass on either side, however whatever color the topmost color is is the preferred passing side. Topmost Green prefer to pass on Starboard (right) Topmost Red prefer to past on Port (left). There are sometimes lit, sometimes lettered, never numbered.
Preferred channel markers are buoys showing red and green bands.
A white buoy with orange bands and an orange diamond is a hazard buoy. Watch out for shoals, rocks, fallen trees, construction, or other hazards.
lp
warning- use caution
In Region B a "green can shaped buoy" stands for the edge of a channel on a boaters left side when entering from open sea or heading upstream, the opposite applies in Region A.
A boat should cruise between a green and red buoy. The red buoy will always be located on the right side of your boat. Red buoys will always mean , returning, red, and right. There will be a number on a red buoy that will give the chart location. The numbers will always be even.
If it's "red right returning", it's green left returning and green right (starboard) going. That is to say, you pass it to the left (port) as you return to port.
In Region B a "green can shaped buoy" stands for the edge of a channel on a boaters left side when entering from open sea or heading upstream, the opposite applies in Region A.
Do not pass between the buoy and the shore
Danger.
When going upstream, a buoy with a number 5 and flashing green light indicates the presence of a dam ahead. The dam may be used to generate hydroelectric power or to provide water for irrigation, and can pose a danger to boats and other vessels.
A yellow buoy in the water means caution. They can mean there is danger of pipes, dredge lines or other dangers.