reddit immigrant question - Lemmy.world

Hello there, happy to be here and leaving reddit. Trying to figure out lemmy.world and fediverse through jerboa and I have a question. In the comments I see some comments with a red, green or light blue line on the left side. I haven’t figured out its meaning from any pattern yet, and google didn’t help. Can someone explain it to me? Thanks, and I hope I’m making my first post correctly!