I was using a physical RGB LED so there wasn't much extra bandwidth for conveying information. I live in a cold climate so green really meant "Leave now and you'll only have to wait in the cold at the stop for 2-3 minutes". Here's the code if anyone's interested[1]. Looks like my memory wasn't quite right, I did blue/green/red with blue=wait, green=leave, red=missed.

[1] https://gist.github.com/kevana/32bfa486d9fb0aa20a19694d1b69d...