JSFiddle - React, Tailwind, and code Playground

HTML

<h2 class="fake-class">fake-class will be green</h2>

	<h2 class="">empty class SHOULD be white</h2>

	<h2>no class should be red</h2>

	<h2 class="fake-clas2s">fake-class2 SHOULD be white</h2>

	<h2 class="">empty class2 SHOULD be white</h2>

	<h2>no class2 SHOULD be red</h2>

CSS

h2 {
    color:#fff
}
:not([class]) {
    color:red;
    background-color:blue
}
.fake-class {
    color:green
}