JSFiddle - React, Tailwind, and code Playground

HTML

<span><select>
<option value="volvo">Volvo</option>
<option value="saab">Saab</option>
<option value="opel">Opel</option>
<option value="audi">Audi</option>
</select><span></span></span>

<p><strong>Note:</strong> The autofocus attribute of the select tag is not supported in Internet Explorer 9 and earlier versions, or in Firefox.</p>

CSS

span {
    position:relative;
    z-index:0;
}
span span {
    display:none;
    content:"";
    position:absolute;
    top:0;
    left:0;
    right:0;
    height:100px;
    background:rgba(255, 0, 0, .25);
    z-index:-1;
}
span select:focus + span {
    display:block;
}