If you see a red, a green, and a white light on another boat, what does this indicate?

Seeing a red, a green, and a white light on another boat indicates that you are likely facing a situation where the other vessel is approaching you head-on. The red light indicates the port side of the other vessel (left side), while the green light indicates the starboard side (right side). The presence of both colored lights along with a white light, typically positioned higher, conforms to the navigation rules for vessels underway. This configuration signals that the other boat is likely moving towards you and requires appropriate actions, such as determining who has the right of way based on navigation rules.