Hi Jonathan,

Here you are:

$(document).ready(function(){
  $('.collection').on('change', 'input', changeColor);
  $('.normalField').on('change', 'input', changeColor);
  function changeColor () {
    if ($(this).val() != '') {
      $(this).css('background','#ffff99');
    }
    else {
      $(this).css('background','none');
    }     
  }
});

This seems to work to your description, where the collection is given the class "collection". It changes only the color of the field that the parent is filling/clearing information from as you would expect.

Just noting that I tried targeting the field directly (#q4 in my case), but that didn't work as I wanted.

$(document).ready(function(){
  $('.collection').on('change', 'input', changeColor);
  function changeColor () {
    if ($('#q4 input').val() != '') {
      $('#q4 input').css('background','#ffff99');
    }
    else {
      $('#q4 input').css('background','none');
    }     
  }
});

As you can see, if the parent added multiple collections before filling any of the fields out, filling in one field would change the color of even the blank ones. Not to mention that the color wouldn't clear unless all of the fields in each collection was blank. 

Hope this helps.