Why is a section in my DOC appearing in red?

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.