JSFiddle - React, Tailwind, and code Playground

HTML

<link rel="stylesheet" href="//code.jquery.com/ui/1.12.0/themes/smoothness/jquery-ui.css">
  <script src="//code.jquery.com/jquery-1.12.4.js"></script>
  <script src="//code.jquery.com/ui/1.12.0/jquery-ui.js"></script>
<body>
 
<ul id="selectable">
  <li>Item 1</li>
  <li>Item 2</li>
  <li>Item 3</li>
  <li>Item 4</li>
  <li>Item 5</li>
</ul>
 
<script>

$( "#selectable" ).selectable({
  start: function( event, ui ){
   var el = document.querySelector('.ui-selected');
  	if(el) {
		 el.classList.remove('ui-selected')
    }
  }
});
</script>

CSS

#selectable .ui-selecting {
    background: #ccc;
  }
  #selectable .ui-selected {
    background: #999;
  }