Code Reference:
<div class="modal in" id="criticalModal" style="align-items: center; padding-left: 7px; transform: translate(0%, 25%);">
<div class="modal-dialog">
<div class="modal-content">
<div class="modal-header" style="padding-bottom: 0px; background-color: ##c0c307 !important;">
<h5 class="modal-title" style="font-family: Dubai;font-weight: bold;font-size: 20px;text-align:center;margin-bottom: 12px;">Custom Pop up Message</h5>
</div>
<div class="modal-body" style=" padding: 25px;">
<p style="font-family: Dubai; font-size: 12px;">Kindly be informed that SailPoint portal provides access governance capabilities.</p><div class="line-break" style="height: 0.6em;"></div><p style="font-family: Dubai; font-size: 12px;">Write more about your custom message.</p>
</div>
<div class="modal-footer" style="padding: 10px;background-color: white;border: none;text-align: center;">
<button type="button" class="btn btn-danger" style="font-family: Dubai;background-color:#B00020" data-dismiss="modal">Acknowledge</button>
</div>
</div>
</div>
</div>
Customization needs to be perfomed on ngAppPage.xhtml page to achive the use case.