JSFiddle - React, Tailwind, and code Playground

HTML

<div class="tab">
    <button onclick="changeColor(event)">Click Me</button>
 </div>

CSS

.tab button {
    background-color: yellow;
}

/* Create an active/current tablink class */
.tab button.active {
  background-color: red;
}

JavaScript

function changeColor(evt){
	evt.currentTarget.className += "active";
}