There are two possible reason for this:
Your section is empty (besides check boxes, remarks section..), so the application reminds you that the static section is not filled in or the dynamic section has no item selected:
To remove it, simply fill in the section and it’ll become grey.
Note: When printed without any selected input there will be “not applicable” below the section title (instead of no input selected)
You have a search specified in the configuration options of that section which is used to find the items to insert and the selected elements are not up to date:
To remove it, simply press the double arrow button to Update the selection of items.
For more information, see Items selection by search.