Where may red or green lights appear?

Red or green lights are used in navigation to indicate the position and direction of vessels and to mark channels and hazards. Specifically, they appear on horizontally-banded buoys, which are used to mark navigable waterways and indicate navigational aids. The colors signify the lateral system: red generally indicates the left side when entering a channel from the sea, while green indicates the right side.

In the case of horizontally-banded buoys, the bands themselves are typically painted in red and green to visually convey the lateral marks, and the lights atop these buoys will match the color of the bands to provide nighttime navigation guidance. This system is vital for mariners as it helps them understand their relative position in relation to the buoy and navigate safely.

Other options do not accurately reflect where red and green lights are commonly used within maritime navigation systems. For example, signal flags are used for communication, while vessels at anchor may display lights for visibility but do not typically utilize red and green lights for navigation. Navigational markers encompass a broad range of aids that can include lights, but the question is specifically asking for where red or green colors are definitively associated with lighting systems.