JSFiddle - React, Tailwind, and code Playground

HTML

<div class="red placeholder"></div>
<div class="blue placeholder"></div>
<div class="green placeholder"></div>

CSS

.placeholder {
    width: 100px;
    height: 100px;
    margin: 10px;
    border: 1px solid black;
}
.placeholder:hover {
    background-color: gray;
}
.red { background-color: red; }
.blue { background-color: blue;}
.green { background-color: green;}