Hi zentral,
I tested the background color, it works fine for me. please try the steps below
1. Link to http://www.cutesoft.net/example/createPDF.aspx
2. Paste the code below into html view
<div style="position: absolute; width: 104px; height: 104px; background-color: #ff6600;">my pdf doc</div>
3. Click the "Submit" button
4. Click the "check the PDF file" link to save the pdf file.
Regards,
Ken