What purpose of Those colorful balls attached to Power Lines?

Those colorful balls that you see attached to power lines are called visibility marker balls.

They are placed on power lines to make the conductor crossings visible to aircraft pilots.

They are spherical markers that weigh about 17 pounds each and are often found near mountain passes, in deep valley areas, near major freeway crossings, and around airports.

The balls allow the electrical wires to be noticeable, especially during times of low visibility or inclement weather.