Red and Green for Open/Closed and Busy/Available

I am facing an interesting issue when realizing an interactive map for one of our customers - an airport.

The map is showing real-time information about the current status of the infrastructure - for example: check-in desks. Currently used check-in desks are displayed in the map using a color, whether free check-in desks are displayed using another color.

Here comes the problem: if we think about the passenger-flow point of view, I would find it natural to display "open" check-in with green color, and "closed" check-in with red.

On the other side, if we think about the terminal-availability point of view, it looks like the more intuitive option would be to display "available" check-in with green color, and "busy" check-in with red.

In other words:

BUSY = OPEN ===> Green Option 1, Red Option 2

AVAILABLE = CLOSED ===> Red Option 1, Green Option 2

Our key-users group is split almost perfectly at 50% between the first and the second option - the result is that everyone is getting confused and they cannot figure out at a glance which is the situation.

It looks obvious that we need to move further and abandon the green/red scheme, but which one could make sense?

Thanks in advance for any suggestion!