JSFiddle - React, Tailwind, and code Playground
HTML
<div id="nav"></div>
CSS
* {
margin: 0;
box-sizing: border-box;
}
#nav {
background-color: red;
width: 100%;
height: 100px;
}
JavaScript
var menu = document.getElementById('nav');
var menuBg = menu.getComputedStyle[backgroundColor];
var rgb = menuBg.replace(/^(rgb|rgba)\(/, '').replace(/\)$/, '').replace(/\s/g, '').split(',');
menu.innerHTML = rgb;