Ok, this isn't what I thought. Display ghosted data shows the envelopes over the wave form. I always want this on in every track, and it is currently on in every track.
My problem is different. In one track, despite the selected Volume envelope, the wave form and the envelopes are dark. Usually, the selected wave form is highlighted (it is in the other tracks).
In the above image you can see that the volume envelope is selected but not highlighted. It's just frustrating. If you click on the volume envelope, it doesn't highlight (I think it thinks that it is already highlighted). So, to get the focus on volume, I shift click pan and then shift click volume.
The problem only exists on this one track.