How can I tell if someone is logged in to a computer remotely or not?

[Nikki5]

I know about the green and blue but I can't figure out which means what and the hovering suggested in previous posts doesn't work.  It just tells me who is assigned to used that PC.  I need to know if someone is remotely logged in, or if they are sat at their desks logged in and I can't find out how to tell this!  Anyone help?

[AshC]

@Nikki5  There may not be any visible signs when someone is using the shared file manager, but when the application is in use you should be able to tell, viewing the icon in your task bar.