33 CFR § 62.33 - Information and regulatory marks.
(a) Information and Regulatory Marks are used to alert the mariner to various warnings or regulatory matters. These marks have orange geometric shapes against a white background. The meanings associated with the orange shapes are as follows:
(1) A vertical open-faced diamond signifies danger.
(2) A vertical diamond shape having a cross centered within indicates that vessels are excluded from the marked area.
(3) A circular shape indicates that certain operating restrictions are in effect within the marked area.
(4) A square or rectangular shape will contain directions or instructions lettered within the shape.
(b) When a buoy is used as an information or regulatory mark it shall be white with two horizontal orange bands placed completely around the buoy circumference. One band shall be near the top of the buoy body, with a second band placed just above the waterline of the buoy so that both bands are clearly visible.