JSFiddle - React, Tailwind, and code Playground

HTML

<ul id="listings">
  <li class="layer block color-blue" id="item-1">1</li>
  <li class="layer block color-red" id="item-2">2</li>
  <li class="layer block color-green" id="item-3">3</li>
</ul>

JavaScript

document.getElementById("listings").addEventListener("click", function(e) {
    var el = e.target;
    if (el.tagName == "LI") { // Use only li tags
        for (i=0; i < el.classList.length; i++) {
            if (~el.classList[i].indexOf('color')) {
                var color = el.classList[i];
                console.log('color class found: '+color);
                break;
            }
        }
    }
});