JSFiddle - React, Tailwind, and code Playground

HTML

<select class="mySelect">
    <option value="1" selected="selected">1</option>
    <option value="2">2</option>
    <option value="3">3</option>
    <option value="4">4</option>
</select>

JavaScript

$('.mySelect').change(function () {
    $(this).find('option').css('background-color', 'transparent');
    $(this).find('option:selected').css('background-color', 'red');
}).trigger('change');