What do red and green sidelights indicate on a vessel?

Red and green sidelights on a vessel are essential components of navigation lighting that help to indicate the position and orientation of a boat on the water. The red light is specifically used to indicate the port side, which is the left side of the vessel when facing forward. Conversely, the green light indicates the starboard side, which is the right side when looking toward the bow of the ship. This system is crucial for ensuring safe navigation, especially during nighttime or low visibility conditions, as it allows other vessels to quickly determine the direction a boat is moving and assess potential collision risks.

Understanding this color coding is important for all boaters, as proper recognition of these lights can prevent accidents on the water. The other options provided do not accurately reflect the standard navigational lighting protocols established by maritime regulations, which makes option B the correct answer in this context.