I live near a major airport and see commercial planes with huge front headlights shining in the night sky. What could they be good for way up in the sky, though? I get that when they are taking off/landing headlights are necessary. Why not give them lights like a boat, with a green in front and a red in back?
It’s for identification, navigation, as well as light. You can tell which way a plane is facing/ which way it’s moving, and which side of the plane you’re looking at based solely on the lights and their color. That’s important for night flights. The other commenter is correct that most planes have lights on either side and the lights correspond to the colors standard for that side. So, right side is green, left side is red, etc.
The article below has more information on what the lights do if you’re interested still.
https://pilotinstitute.com/airplane-lights/