JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://ajax.googleapis.com/ajax/libs/jqueryui/1.7.2/jquery-ui.min.js"></script>
<span id="phrase">Here are some words</span>

JavaScript

var s1 = document.getElementById("phrase");
        var str = s1.innerHTML;
        var newText = "";
        for (var i = 0; i < str.length; i++) {
            if (str[i] == 'e') {
               newText+= str.charAt(i).fontcolor("red");
            }
            else {
                newText += str[i];
            }
        }
        s1.innerHTML = newText;