One Green Light is actually being understood and mutual virtues.
It's having the strangest conversations and laughing at the stupid parts. It's being included in plans with close friends and everyone having fun together. It's being spontaneous and letting the unexpected good moments happen. It's being vulnerable and them hugging you as if telling you they hear you.
Two Green Lights is losing your mind and them being concerned about you. It's hanging out with each other because the relationship is worth having. It's talking through the day or the night because the concept of time doesn't matter. It's having the hard talks and letting each other making jokes afterward since life is too short.