I like all of it except the blue for “busy but available soon”. It’s too “opposite” to the red of “busy”. A friendlier variant on red would make more sense to me.. pink, magenta or a burnt orange, say (although this would require more delicate control of the RGB pins! :-))
So when you are in the room there is a red light hanging from the ceiling. As the end of the meeting gets closer and closer the red can blend into another color.