JSFiddle - React, Tailwind, and code Playground

HTML

<select id="sample">
   <option value="red">Red</option>
   <option value="yellow">Yellow</option>
   <option value="blue">Blue</option>
</select>

JavaScript

document.getElementById('sample').onchange = function(){
   document.body.style.background = this.options[this.selectedIndex].value;
}