JSFiddle - React, Tailwind, and code Playground

HTML

<div id="square"></div>
<div>
  <button onclick="colorRed()">Red</button>
  <button onclick="colorYellow()">Yellow</button>
  <button onclick="colorBlue()">Blue</button>
</div>

CSS

#square {
  height: 200px;
  width: 200px;
  border: 1px solid black;
}