JSFiddle - React, Tailwind, and code Playground

HTML

<h4>Exemple SANS les bordures</h4>
<div class="one"></div><div class="two"></div>
<br/><br/>
<h4>Exemple AVEC les bordures</h4>
<div class="one border"></div><div class="two border"></div>

CSS

body { margin: 40px; }

div { display: inline-block; width: 40%; height: 50px; }

.one { background: #191970; }
.one:hover { border: 1px solid red; }

.two { background: #228B22; }

.border { border: 1px solid transparent; }