We're off work at 5:00PM. I've never tried to say "have a good night" at this time of day. In fact, I wouldn't even say it at all unless I'd like to say it to someone who is heading to bed.
When I'm done at 5:00PM, I usually say "see you tomorrow". Until recently I've never started saying "have a good night" to my colleagues. Even if I say it every day now, I don't feel it's right. However, most of my colleagues will keep saying "have a good night" to each other, so it's better for me to do the same thing.
Also, sometimes when it feels really weird or awkward to say, I will say "have a good one" instead.
Is it appropriate to say "have a good night" to colleagues when done at work? Any better way than saying "see you tomorrow"?
EDIT: I've considered saying "have a nice evening", but I feel it's even worse than saying "have a good night" because people might get the impression that you only wish them well for the evening, and that you don't care if they are good or not after the evening.