This is a known problem when opening older files in FD12 or FD13. To fix it:
Go to Format > Elements
Select Apply a Template
Select the same template the script is written in
Click OK
If that still doesn't work, you can remove the highlights manually on Mac via these steps:
In the toolbar, go to Format > Element Settings
Select any element from the left hand column, like Scene Heading
Select the Font tab at the top of the window, then click Set Font
If you have a blue highlight in the Highlight field, click the blue, select either White or None, then hit OK.
Repeat for every other affected element.
Hit OK in the bottom right when done.
Also, to turn off the highlights on Mores and Continueds:
Go to Document > Mores and Continueds and then Set Font
If you have a Yellow highlight in the Highlight field, click the blue, select either White or None, then hit OK.
If you are on Windows, please contact Final Draft support here so they can fix the file manually for you.