In that case Dave I would say its probably not working correctly, which is a shame because its a great idea.
The colours don't seem to update to light green (completed) at all. They stay as dark green (current) and then only after the game is saved and closed.
When it is loaded again the completed orders change colour to dark green (current).
Also the dark green (current) coloured tasks don't change to white when the task waypoints are dragged to a new location on the map making them future tasks again. They do change to white when a new order is first placed on the map however.
The black bar to indicate the selected task is also not updating dynamically when a different unit or task is selected on the map.
Actually there are a lot of inconsistencies associated with this colour coding, and dynamic updating of the Plan dialogue, which would probably be easier to experiment with yourself, than listening to me trying to explain them.