JSFiddle - React, Tailwind, and code Playground

HTML

<ul id="randomCol">
    <li>test1</li>
    <li>test2</li>
    <li>test3</li>
    <li>test4</li>
    <li class="color">test5</li>
    <li>test6</li>
    <li>test7</li>
    <li>test8</li>
    <li>test9</li>
    <li>test10</li>
</ul>

CSS

li {
     background-color:#FFF;
}

.color {
    background-color:#F00;
}

* {
transition: background-color 1s;
-webkit-transition: background-color 1s;
}

JavaScript

var tid = setInterval(changeUp, 1000);
function changeUp() {
  var i = Math.floor((Math.random()*9)+1);
  $('#randomCol').children().removeClass('color');
   $('#randomCol').children().eq(i).addClass('color');
}