There isn't an easy way to get a background color in MOBI.
One simple approach is to use horizontal rules to separate the text.
In
Kindle Formatting: The Complete Guide Joshua Tallent suggests using tables for pull quotes, for example:
Code:
<div align="center">
<table cellpadding="10" style="margin-left:0;">
<tr><td><hr width="500" /></td></tr>
<tr><td align="center" border="1" style="background-color:#C0C0C0">We must have a concrete idea of anything, even if it be an imaginary idea, before we can comprehend it.</td></tr>
<tr><td><hr width="500" /></td></tr>
</table>
</div>
On the Kindle 2 (and 3?) this will have a background color.