Add class to newly selected tag

I want to add a class to a newly selected option/tag within a select2 multiple select element.

My approach is to use the templateSelection callback, but then the class is added to every selected option/tag when the element is initialized.

Could I use the select2:select to flag a newly added option/tag (like adding a new attribute to the data)?

Thank you very much. All the best, Phantom

HTML

<select id="example" multiple="multiple" style="width: 300px">
    <option value="JAN">January</option>
    <option value="FEB">February</option>
    <option value="MAR">March</option>
    <option value="APR">April</option>
    <option value="MAY" selected>May</option>
    <option value="JUN" selected>June</option>
    <option value="JUL">July</option>
    <option value="AUG">August</option>
    <option value="SEP">September</option>
    <option value="OCT">October</option>
    <option value="NOV">November</option>
    <option value="DEC">December</option>
</select>

Javascript

$('#example').select2({
    placeholder: 'Select a month',
  templateSelection: function (data, container) {
    $(container).addClass('classHighlight');
    return data.text;
  }
});

$('#example').on('select2:select', function(e) {
    console.log('Could I use this event?')
    console.log(e.params.data);
});

fiddle: https://jsfiddle.net/Phantomias/g4ae9xsd/23/