Thanks for your question!
This can indeed be done in Studio by utilising the trigger leave event that is linked to trigger regions.
I have created an example project to help with the explanation, it can be downloaded here: TriggerLeaveExample.ZPP (1.0 MB)
The project has a 3D model of a cube in the center of the tracking image. The cube color will change depending on whether the user is close to the object or far away. This same method can be used to make the user move the device further from the target, in turn making an event run.
The example was developed by surrounding the cube and the target with a trigger region. Along with this, there is also an interaction plane with its relative to property set to Z.screen. Both the trigger region and the interaction plane both have the same trigger tag assigned to them. As seen below -
As the plane is relative to the screen, when the user moves the device out of the trigger region, the plane follows. This causes a trigger leave event as both the plane and the region have the same tag. The trigger leave event can be accessed multiple ways, scripting or actions.
For this example, we have chosen to use actions. These actions activate the specific grey/red cube states based on whether the trigger enter or trigger leave event is called.
Hope this helps and please let us know if you have any further questions on this.
All the best,