JSFiddle - React, Tailwind, and code Playground

HTML

<div class="test">Наведи на меня</div>
<div class="bg"></div>

CSS

.test{
    float:left;
    background:green;
    width:100px;
    height:100px;
}

.bg {
    background: #ccc;
    width:500px;
    height:500px;
}

.test:hover + .bg {
     background: #000;
}