What is the four standard light colors used for lighted aids to navigation?

The standard light colors used for lighted aids to navigation are primarily white, red, green, and yellow. Among these, yellow plays a significant role in certain navigational contexts. Specifically, yellow is used for special marks, which indicate specific areas such as spoil grounds or anchorage areas, distinguishing them from other navigational aids. This helps mariners understand the types of navigational channels they are navigating and the nature of the waters they are in.

The other colors listed—purple, orange, and blue—are not standardly used in the context of lighted navigational aids as defined by the United States Coast Guard regulations. Each of the standard colors (white, red, green, and yellow) serves distinct purposes: for example, red is typically used to mark port sides, while green is used for starboard sides. Understanding these distinctions is crucial for safe navigation.