JSFiddle - React, Tailwind, and code Playground

HTML

<h1>This is my Title</h1>
<h1>Another Similar Title</h1>
<div class="color"><h1>Just Title</h1></div>

CSS

h1 {
    text-align: center;
    position: relative;
    font-size: 30px;
    z-index: 1;
}
h1:after {
	content: '';
	background-color: red;
	height: 1px;
	display: block;
	position: absolute;
	top: 18px;
	left: 0;
    width: 100%;
}
.color {
    background-color: #ccc;
}