What's greyed out?
The top and base constraints. Cannot select/adjust them.
Is it in a Model Group?
It was in a model group. For some reason you cannot adjust this setting of the column in the model group even if the model group is in edit mode.
To fix I delete the column from the group and then out it outside the group and then add it back in.
So, the answer to my 2nd question is "Yes". 😉
BTW, you can adjust a grouped column by Editing the Group.
Why can't you edit a columns base and top level when it's in a model group?