What do red and green lights on a vessel indicate at night?

The red light indicates the port (left) side of a vessel, while the green light indicates the starboard (right) side. This color coding is crucial for night navigation and helps in recognizing a vessel's orientation and direction of travel from a distance. When two vessels are approaching each other at night, the color of their navigation lights allows each vessel to determine which side to give way to, as the red light will always be on the left and the green on the right. This system of color-coded lights establishes clear visual communication between vessels and enhances safety at sea by preventing collisions.

Understanding this system is essential for boat operators and navigators, as it is part of the international regulations for preventing collisions at sea. This ensures that all mariners adhere to a standardized way of identifying and interacting with other vessels, especially in low-visibility conditions. Other options provided do not accurately describe the established convention for navigation lights and their meanings, leading to confusion about safe navigation practices.