JSFiddle - React, Tailwind, and code Playground

HTML

<ul>
    <li><input type="text" id="c1" class="casella" /></li>
    <li><input type="text" id="c2" class="casella" /></li>
    <li><input type="text" id="c3" class="casella" /></li>
</ul>
<input type="button" onclick="javascript:coloraCaselle('casella', '#f00');" value="Colora le caselle" />

JavaScript

window.coloraCaselle = function (nomeClasseCss, colore) {
    var caselle = document.getElementsByClassName(nomeClasseCss);
    for (var i = 0; i < caselle.length; i++) {
        caselle[i].style.backgroundColor = colore;
    }
}