JSFiddle - React, Tailwind, and code Playground

HTML

<ul class="logoUl">
    <li class="grey">Test 1</li>
    <li class="grey">Test 2</li>
    <li class="grey">Test 3</li>
    <li class="grey">Test 4</li>
</ul>

JavaScript

var strString = "orange,blue,green,pink",
    strArray = strString.split(',');

$("ul.logoUl > li")
    .removeClass() // first remove previous class
    .addClass(function (index) { // then add new class
        return strArray[index];
    });

console.log($('ul li'));