JSFiddle - React, Tailwind, and code Playground

HTML

<div id="text" contenteditable="true">O </ div>

CSS

.green {
  color: green;
}

JavaScript

var text = document.getElementById('text');

text.onkeyup = function(evt) {
  if (this.textContent.indexOf("Brasil") > 0) {
    text.innerHTML = this.textContent.replace("Brasil", "<b class='green'>Brasil<b>");
  }
};