In a power-driven vessel at night, seeing a green and a white light means you are the:

When you see a green light and a white light on a power-driven vessel at night, it indicates that you are the stand-on vessel. In maritime navigation, the stand-on vessel is one that has the right of way in a crossing situation. It is expected to maintain its course and speed, allowing the other vessel to take action to avoid a collision.

The green light typically indicates the starboard side of the vessel, while the white light is a masthead light. The configuration of these lights suggests that the other vessel is approaching from your starboard side, which means you should continue on your current path. The stand-on vessel has a responsibility to navigate safely but is also expected to react effectively if it becomes apparent that a collision might occur, even if it is the stand-on vessel.

This concept is fundamental to ensuring safe navigation and right-of-way rules on the water, helping to prevent accidents between vessels at night.