Add css class to dropdown

Question

This is a dropdown with two items. I want to visually give these two items a css style. Is this possible? This is the code I used:

 (function($) {
    "use strict";   
    
       tinymce.PluginManager.add( 'mybutton', function( editor, url ) {
          
          editor.addButton( 'mybutton', {
            text: tinyMCE_object.button_name,
             type: 'listbox',
             icon: false,
             title:  'Shortcodes',
             onclick : function(e) {},
             values: [
                {text:'update',
                onclick:function(){
                   editor.insertContent( '[update][/update]');
                }},
                {text:'other',onclick:function(){
                   editor.insertContent( '[other][/other]');
                }},
             ]
          });
    
       });
    
    })(jQuery);

My current dropdown menu:

I've read this post but I have no idea how I can translate that to my dropdown.