Here is how to highlight form text items, witch Value Required attribute is set to "Yes" and do not have any value.
Create dynamic action to page zero
Now run application and items having Value Required set to "Yes" background color is changed if item do not have any value.
You can find Value Required setting from item attributes.
If you do not like use this for all your application items, you can create dynamic action to specific page(s). Or if you do not use item Value Required setting, you can use e.g. Item as Selection Type for dynamic action and specify items you like highlight.
See working example.