JSFiddle - React, Tailwind, and code Playground

HTML

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

CSS

div { height: 20px; width: 20px; }

.red.red { background-color:red; }
.red.blue { background-color:green; }
.red .blue { background-color:yellow; }
.blue { background-color:blue; }