What do red buoy's and green buoy's mean when boating?

It depends on where you are in the world.

The International Association of Marine Aids to Navigation and Lighthouse Authorities (IALA) "B" region (Covers the America's, Japan, S. Korea and the Philippians). In IALA "B" the red buoys are on the right side of the channel and green on the left side of the channel when returning from sea.

In the US a good memory tool is "Red right return".

In the IALA "A" region (The rest of the world) Green buoys are on the right side of the channel and the red buoys are of the left side of the channel when returning from sea.

They are called lateral marks and they are used to mark the outer boundaries of the navigational channel.