Final answer:
Operators of power-driven boats can tell they are approaching each other head-on when they see red and green navigation lights. When these lights are seen in line ahead, it indicates a head-on situation and both boats should alter their course to right to avoid a collision.
Step-by-step explanation:
At night, operators of power-driven boats can tell they are approaching each other head-on when they see red and green navigation lights. The red light is on the port (left) side of the boat, and the green light is on the starboard (right) side of the boat. When the red and green lights are seen in line ahead, it indicates that two boats are approaching each other in a head-on situation. This means that both boats should alter their course to starboard (right) to avoid a collision.