Changing background colour

Hey folks,

When a product category is empty (like the PC section with the default install) it creates a div called middle which sets the background colour to white. I can not find this anywhere in the stylesheet so im guessing its hard coded, just can't find out which file its hard coded in to?

<div class="top">
</div>
<div class="middle">
<div style="border: 1px solid rgb(221, 221, 221); padding: 10px; background: rgb(186, 202, 51) none repeat scroll 0% 0%; -moz-background-clip: -moz-initial; -moz-background-origin: -moz-initial; -moz-background-inline-policy: -moz-initial; margin-bottom: 10px;">There are no products to list in this category.</div>

It's in template/error/not_found.tpl