33 CFR § 62.51 - Western Rivers Marking System.
(a) A variation of the standard U.S. aids to navigation system described above is employed on the Mississippi River and tributaries above Baton Rouge, LA and on certain other rivers which flow toward the Gulf of Mexico.
(b) The Western Rivers System varies from the standard U.S. system as follows:
(1) Buoys are not numbered.
(2) Numbers on beacons do not have odd/even lateral significance but, rather, indicate mileage from a fixed point (normally the river mouth).
(3) Diamond-shaped non-lateral dayboards, checkered red-and-white or green-and-white, similar to those used in the U.S. Aids to Navigation System, as appropriate, are used as crossing dayboards where the river channel crosses from one bank to the other.
(4) Lights on green buoys and on beacons with green daymarks show a single flash which may be green or white.
(5) Lights on red buoys and on beacons with red daymarks show a double flash [Group Flashing (2)] which may be red or white.
(6) Isolated danger marks are not used.