The issue is that I need to use this script on multiple fields (with the same CSS class) within the same form. What syntax changes need to be made? Right now -- this script will work for the first field you click in -- but won't work for the other fields in the same form.
Your script should work if the IDs of all your text fields are unique.
However, I do see something not-so-optimal in your script. Every time a text field is focused you add a brand new event listener to that field on the "blur" event. You should add the blur event listener at the same time you add the focus event listener (i.e. only one time).