JSFiddle - React, Tailwind, and code Playground

HTML

<button>Random color</button>
<p class="text">Some text</p>

CSS

.text {
  color: var(--text-color)
}

JavaScript

function r() {
	return Math.floor(255 * Math.random())
}

function assignColor() {
	document.body.style.setProperty('--text-color', `rgb(${r()},${r()},${r()})`);
}

assignColor();

document.querySelector('button').addEventListener('click', assignColor);