UFOs lights at night. Why?

I’ve been pondering this question for about a week now. I’m not sure if it’s been discussed before but… The question is: Why do UFOs have bright lights when they’re seen at night?

Many people who report UFO sightings at night describe the craft as having lights all around or being a ball (or other shape) of light. Some witnesses mention rainbow-colored lights, while others note neutral colors or changing lighting patterns. Could these lights be related to how they power their crafts? Do they use light in some way for propulsion or levitation? Or is it a byproduct of their antigravity technology, or their interaction with our reality assuming they’re interdimensional beings? Or even, could the lights be a safety measure, meant to make their presence known to our aircraft and avoid collisions?

My wild guess is that the lights are byproduct of their crafts propulsion system and or their interaction with our atmosphere.

What do you guys think?