Office 365 Exchange + Office 365 Outlook: Warning banner is not displaying colours - outlook

Question

I'm working on a warning banner to be displayed for our users to warn them not to click the links or attachment in a suspicious email, so that they can be warned about any phishing or spoofing. This is by using the "prepend a disclaimer" rule in exchange online.
I've followed a tutorial on prepending this banner onto an email but Outlook doesn't seem to render the background colours on the table? It just displays the text content only.
Code is here:
<!-- Yellow caution banner -->
<table border=0 cellspacing=0 cellpadding=0 align="left" width="100%">
<tr>
<!-- Remove the next line if you don't want the Yellow bar on the left side -->
<td bgcolor="#ffb900" style="background-color:#ffb900;padding:5pt 2pt 5pt 2pt"></td>
<td width="100%" bgcolor="#fff8e5" cellpadding="7px 6px 7px 15px" style="background-color:#fff8e5; padding:5pt 4pt 5pt 12pt; word-wrap:break-word; font-family:sans-serif">
<div style="color:#222222;">
<span style="color:#222; font-weight:bold;">Caution:</span>
This is an external email and has a suspicious subject or content. Please do not click on any links or download any files unless you know the sender and you are expecting this message. If you are unsure, please contact the IT Helpdesk.
</div>
</td>
</tr>
</table>
<br />
I'm trying to get it to look like this:
(https://i.stack.imgur.com/yltQ7.png)
But I receive this instead.
(https://i.stack.imgur.com/3fiZx.png)
It doesn't seem to matter whether dark mode is enabled or not. As far as I know, HTML is enabled in outlook.
Thanks in advance for any help with this.

Answer 1

Didn't work to me as well. Try this:
<table border=0 cellspacing=0 cellpadding=0 align="left" width="100%">
<tr>
<!-- Remove the next line if you don't want the Yellow bar on the left
side -->
<td style="background:#ffb900;padding:5pt 2pt 5pt 2pt"></td>
<td width="100%" cellpadding="7px 6px 7px 15px" style="background:#fff8e5;padding:5pt 4pt 5pt 12pt;word-wrap:break-word">
<div style="color:#222222;">
<span style="color:#222; font-size:13px; font-weight:bold;">CAUTION:</span>
<span style="color:#222; font-size:13px;">This email is from an external source. Do not click links or open attachments unless you recognize the sender and know the content is safe. When in doubt, contact Nova IT department
</div>
</td>