JSFiddle - React, Tailwind, and code Playground

HTML

<button id="btnAdd">Add</button>
<div class="panel-footer">
    <div class="post-activity">
        <i class="loading-icon"></i>
        <button id="btnChange">Change Color</button>
    </div>
</div>

CSS

.comments-ch {
    width: 100px;
    height: 100px;
    background-color: #00CC00;
}

JavaScript

$("#btnChange").click(function() {
    ChangeColor(this);
});
function ChangeColor(element)
{
    $(element).closest(".panel-footer").find(".comments-ch").css("background-color","#CC0000");
}
$("#btnAdd").click(function(){
    var $div = $("<div>").addClass("comments-ch");
    $(".panel-footer").append($div);
});