There are multiple ways to do this...

A simple one would be to make an copy of the form that is used for archival to your repository and only include the highlighting on that version of the form.

Here's another method that doesn't include the alternate form.

For this, you add the "highlightAfter" class to any field you want highlighted after submission.

This CSS does the actual highlighting: 

.highlightAfter {background-color : yellow;}

And this Javascript removes the highlighting from the fields while the form is active:

$(document).ready(function () {
  
  //Find input fields with highlightAfter class and remove it.
  //This allows the highlighting only on the submitted form, but not the active form.
  $('.highlightAfter input').closest('.form-q').removeClass('highlightAfter');
  
  //Find select (dropdowns) fields with highlightAfter class and remove it.
  //This allows the highlighting only on the submitted form, but not the active form.
  $('.highlightAfter select').closest('.form-q').removeClass('highlightAfter');
  
  //Find textarea (multi-line) fields with highlightAfter class and remove it.
  //This allows the highlighting only on the submitted form, but not the active form.
  $('.highlightAfter textarea').closest('.form-q').removeClass('highlightAfter');
  
});

This method has a benefit over the method of using a different form for archival, that it will also work on the read-only view inside forms of submitted tasks.

Edit to add: @████████'s suggestion is more elegant than mine.