JSFiddle - React, Tailwind, and code Playground

HTML

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

CSS

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

.red,
.red:hover { background-color: red; }

.blue,
.blue:hover { background-color: blue;}

.green,
.green:hover  { background-color: green;}