JSFiddle - React, Tailwind, and code Playground

by gfg

HTML

<select id="HOT_ColorsTheme">
    <option value="A">A</option>
    <option value="B">B</option>
</select>

<div class="Today" style="width: 200px; height: 200px;border: 1px solid #000000"></div>

JavaScript

function changeColor() {
        var sel = $('#HOT_ColorsTheme').val();
        if (sel=='A') {
             $(".Today").css({'background' : '#fe0002', 'color' : '#000000'});
        }
        if (sel=='B') {
             $(".Today").css({'background' : '#dedede', 'color' : '#000000'});
        }
    }

 $("#HOT_ColorsTheme").on('change', changeColor);
        $(document).ready(function() {
            changeColor();
        });