Code of Federal Regulations Title 33. Navigation and Navigable Waters § 33.62.43 Numbers and letters

(a) All solid red and solid green aids are numbered, with red aids bearing even numbers and green aids bearing odd numbers. The numbers for each increase in the Conventional Direction of Buoyage. Numbers are kept in approximately sequence on both sides of the channel by omitting numbers where necessary.

(b) Only sidemarks are numbered. However, aids other than those mentioned above may be lettered to assist in their identification, or to indicate their purpose. Sidemarks may carry letters in addition to numbers to identify the first aid to navigation in a waterway, or when new aids to navigation are added to channels with previously completed numerical sequences. Letters on sidemarks will follow alphabetical order from seaward and proceeding toward the Conventional Direction of Buoyage and will be added to numbers as suffixes.

(c) Aids to navigation may be fitted with light-reflecting material to increase their visibility in darkness. The colors of this material may convey the same significance as the aid except that letters and numbers may be white.

(d) Exceptions to the provisions of this section will be found on the Western Rivers System. See § 62.51.

(e) The guidelines for the display of numbers and letters on aids to navigation are identical for both Region A and Region B;  red aids to navigation display even numbers, and green aids display odd numbers.