JSFiddle - React, Tailwind, and code Playground

HTML

<html>
<head></head>
<body>

<select id="select_color" tabindex="1" name="select_color">
    <option value="white">Белый</option>
    <option value="red">Красный</option>
    <option value="blue">Синий</option>
    <option value="white">Черный</option>
</select>

<div class="box red">Text</div>

</body>
</html>

CSS

.box {
    width: 200px;
    height: 200px;
    border:#DDDDDD 1px solid;
}

.white {background: #fff;}
.red {background: #f00;}
.blue {background: #00f;}
.black {background: #000;}

JavaScript

var xXx = document.querySelector('.box');
var select = document.getElementById('select_color');

select.onchange = function(){
    xXx.style.background = select.options[select.selectedIndex].value;
}