JSFiddle - React, Tailwind, and code Playground

HTML

<p id="exmpl" class="green">Пример</p>
<button id="button">Сменим цвет</button>

<script>
    document.getElementById('button').onclick = function() {
    document.getElementById('exmpl').className="red";}
</script>

CSS

.green {color: green;}
.red {color: red;}