JSFiddle - React, Tailwind, and code Playground

HTML

<div class='box'></div>
<div class=' red box'></div>
<div id='red' class='box'></div>
<div class='box'></div>
<div class='box'></div>

CSS

.red{
    background:red;
}
#red{
    background:red;
}

.box{
    width:50px;
    height:50px;
    background:dodgerblue;
    margin:5px;
}