The AP disengage bar isn't a toggle switch IRL. It should stay in the new position when you click on it.
E.g. if the bar is moved to the down position, it should stay down (and hence prevent AP engagement).
In the 747 in the down position (movement should be animated the same way as in the 777) it should reveal an amber area.
In the 777 this area is painted amber with black stripes.