If you want to prevent a measure from being included in the traffic light calculations, you can simply pause it. To do this, proceed as follows:
In the tree, right-click on the desired measure (it also works on a measure package/project/program level).
In the right-click menu, select the option "Pause / Activate". You can tell that the task is paused by the crossed-out traffic lights in the tree.
If you want to include the measure in the aggregation again, proceed in the same way.
Note: Pausing/activating the aggregation is inherited downwards in the tree. For example, you can pause an entire measures package with just one click.