How to make a popup on a node's content using the colorbox module?
For creating pop-up's in colorbox, you can simply use Bootstrap Modal Window.

Don't forget to include the below ones:
1. bootstrap.min.css 
2. jquery.min.js 
3. bootstrap.min.js 

FULL WORKING CODE: 

&lt;!DOCTYPE html&gt;
&lt;html lang="en"&gt;
&lt;head&gt;
  &lt;title&gt;Bootstrap Example&lt;/title&gt;
  &lt;meta charset="utf-8"&gt;
  &lt;meta name="viewport" content="width=device-width, initial-scale=1"&gt;
  &lt;link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/css/bootstrap.min.css"&gt;
  &lt;script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"&gt;&lt;/script&gt;
  &lt;script src="https://maxcdn.bootstrapcdn.com/bootstrap/3.3.7/js/bootstrap.min.js"&gt;&lt;/script&gt;
&lt;/head&gt;
&lt;body&gt;

&lt;div class="container"&gt;
  &lt;h2&gt;Small Modal&lt;/h2&gt;
  &lt;!-- Trigger the modal with a button --&gt;
  &lt;button type="button" class="btn btn-info btn-lg" data-toggle="modal" data-target="#myModal"&gt;Open Small Modal&lt;/button&gt;

  &lt;!-- Modal --&gt;
  &lt;div class="modal fade" id="myModal" role="dialog"&gt;
    &lt;div class="modal-dialog modal-sm"&gt;
      &lt;div class="modal-content"&gt;
        &lt;div class="modal-header"&gt;
          &lt;button type="button" class="close" data-dismiss="modal"&gt;&amp;times;&lt;/button&gt;
          &lt;h4 class="modal-title"&gt;Modal Header&lt;/h4&gt;
        &lt;/div&gt;
        &lt;div class="modal-body"&gt;
          &lt;p&gt;This is a small modal.&lt;/p&gt;
        &lt;/div&gt;
        &lt;div class="modal-footer"&gt;
          &lt;button type="button" class="btn btn-default" data-dismiss="modal"&gt;Close&lt;/button&gt;
        &lt;/div&gt;
      &lt;/div&gt;
    &lt;/div&gt;
  &lt;/div&gt;
&lt;/div&gt;

&lt;/body&gt;
&lt;/html&gt;