[Lynne]

There is no option to do this. If you want to do it for all the moderator posts, then you can put a condition in to add a class to the div if the post is by a mod and then add a background color to the class in the additional.css template.

<vb:if condition="is_member_of($post, 5,6,7)">modclass<vb:if>
and
.modclass {background: pink;}

(This has actually been covered a few times before.)