JSFiddle - React, Tailwind, and code Playground

HTML

<body id="top" class="grid-body mode-article">
<div class="blockgroup content-width">test</div>
</body>

CSS

:root {
  --testbg: pink;
  --testcolor: red;
}

.content-width {
	background: var(--testbg);
	color: var(--testcolor);
}

.grid-body.mode-article {
  --testbg: green;
}

.mode-article {
  --testcolor: blue;
}