HTML

How to add button with url?

Message <a class="aui-button" href="http://google.com/">Button</a>

How to change the text color?

<text style="color:black">Message</text> <a class="aui-button" href="http://google.com/">Button</a>
<text style="color:#000000">Message</text> <a class="aui-button" href="http://google.com/">Button</a>

JavaScript

How to add JavaScript to banner?

Add to message <script/> tag:

message text
<script>
//JavaScript code
alert('test')
</script>