Use the class mzp-t-error for a negative notification, to indicate an unsuccessful action. This example also features an action link.

<aside class="mzp-c-notification-bar mzp-t-error">
    <p>Error! Something has gone horribly wrong. <a href="#" class="mzp-c-notification-bar-cta">Undo?</a></p>
</aside>