JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://code.jquery.com/jquery-3.2.1.min.js"></script>
<button id="changeColorButton" class="btn-secondmenu">Button</button>


        <select name="colors" id="changeColorSelect">
                <option value="red">Red</option>
                <option value="green" selected="selected">Green</option>
                <option value="yellow">Yellow</option>
                <option value="black">Black</option>
        </select>

JavaScript

$('#changeColorButton').click(function() {
	var color = $('#changeColorSelect').val();
	console.log(color)
  $('body').css("background-color",color);
})