Final answer:
Seeing a green light while boating at night indicates that you are approaching the starboard side of another vessel, and you should give way to avoid a collision.
Step-by-step explanation:
If you see only a green light while boating at night, you may be approaching a starboard side of another vessel. According to navigation rules, green lights are displayed on the starboard (right) side of a boat and a red light is on the port (left) side. Therefore, if you see a green light, it means that you are on a collision course with the starboard side of another vessel. The correct approach in this situation is to give way to the other vessel, as per the 'port-side rule', which dictates that vessels approaching from the port side should give way to those on the starboard.