What color is the starboard sidelight on a ship?

The starboard sidelight on a ship is green. This color coding is part of the International Regulations for Preventing Collisions at Sea (COLREGs), which set standards for vessel navigation and signaling. The green color indicates the right side of a vessel when facing the bow, helping to identify the direction the ship is heading in low visibility conditions.

This convention is vital for preventing collisions at sea, as it allows other vessels to determine the orientation and status of nearby ships based on the lights they display. Consequently, when you see a green light from another vessel, it informs you that vessel's starboard side is facing you. Understanding this is crucial for maritime navigation and safety.