Channel markers are coloured red and green to indicate which side of your vessel you should pass them on.
When proceeding outbound:
Pass the red channel markers on your vessel's starboard side (the starboard side is the right hand side of your boat when facing the bow).
Pass the green channel markers to port (the port side is the left hand side of your boat when facing the bow).
When proceeding inbound, do the opposite:
Pass the red channel markers on your vessel's port side and.
Pass the green channel markers to starboard.