Entry 1 Red and green, and which side to favor
In most regions, red markers mark one side of a channel and green the other, and the long-standing guidance of keeping red markers on a particular side when returning from open water toward a harbor is still the quickest mental shortcut most boaters rely on.
Entry 2 Shapes carry meaning too
Beyond color, the shape of a marker — square versus triangular, or a numbered can versus a nun buoy — reinforces which side of a channel it marks, which matters at a glance in low light or choppy water when color alone is harder to judge accurately.
Entry 3 Markers that aren't about channels at all
Not every marker defines a channel edge. Some mark a hazard directly, some indicate a safe-water area in the middle of a channel, and some are purely informational. Learning to recognize these as a separate category avoids misreading a hazard marker as a channel edge.
Entry 4 Questions people ask
Does marker color convention differ by region?
Yes — conventions differ between regions of the world, so it is worth confirming the local system when boating somewhere unfamiliar.
What should I do if a marker seems out of place or damaged?
Treat the charted position as authoritative over a visibly displaced marker, and report it to the relevant local authority if it looks damaged or missing.