A power-driven boat less than 50 meters in length must display red and _____________________ sidelights, a masthead light, and a _____________________ light.

For a power-driven boat less than 50 meters in length, the correct configuration of navigation lights is crucial for safety and compliance with the International Regulations for Preventing Collisions at Sea (COLREGs). Such a vessel is required to display red and green sidelights. The red light is displayed on the port (left) side, while the green light is on the starboard (right) side. Additionally, it must have a masthead light and an all-round white light.

Displaying the red and green sidelights ensures that other vessels can determine the orientation and direction of travel of the power-driven boat. The masthead light, which is white, provides additional visibility from ahead, while the all-round white light is used when the vessel is at anchor or underway in certain conditions. This standardized lighting arrangement helps prevent collisions by allowing other mariners to accurately assess the boat's position and heading.

The other color choices are not correct for the sidelights of a power-driven vessel of this size, as they do not conform to the regulations outlined for navigation lights. Therefore, the specified red and green sidelights effectively communicate essential navigational information to other vessels on the water.