JSFiddle - React, Tailwind, and code Playground

HTML

<div onmouseenter="mOvr(this,'#A8A8A8', event);" onmouseleave="mOvr(this,'#ffffff', event);">
    <div>Passa aqui o mouse</div>
</div>

CSS

div {
    width: 200px;
    height: 100px;
    padding: 20px;
}

JavaScript

function mOvr(src, clrOver, event) {
    src.style.backgroundColor = clrOver;
}