JSFiddle - React, Tailwind, and code Playground

HTML

<div id="some-div">
</div>

CSS

#some-div {
    width: 100px;
    height: 100px;
    
    background-color: rgba(100,100,0,0.2);
    transition: background-color 0.5s ease;
}
#some-div:hover { background-color: rgba(100,0,0,0.7); }