JSFiddle - React, Tailwind, and code Playground

HTML

<div id="div1">Hover me!</div>
<div id="div2"></div>

CSS

div{
    width: 200px;
    height: 200px;
    background-color: black;
    margin: 10px;
    color: white;
    text-align: center;
    line-height:200px;
    font-size: 36px;
}

#div1:hover + #div2{
    background-color: blue;
}