4
Oops!
This is my fault for quickly glancing over your post instead of reading it properly. Shame on me

.
You are correct in that header.php specifies the newbb.css file and assigns it to $newbb_module_header.
I can then see a few
le="color: #000000"><?php $xoopsTpl->assign('xoops_module_header', $newbb_module_header);
in index.php, viewall.php etc.
I went to a forum post and looked at the HTML source but could only see a single newbb.css reference.
le="color: #000000"><?php <link rel="stylesheet" type="text/css" media="screen" href="http://xasset.co.uk/xoops.css" /> <link rel="stylesheet" type="text/css" media="screen" href="http://xasset.co.uk/themes/xasset/styleNN.css" /> <!-- RMV: added module header --> <link rel="alternate" type="application/xml+rss" title="Discussion Forums" href="http://xasset.co.uk/modules/newbb/rss.php" /> <link rel="stylesheet" type="text/css" href="templates/newbb.css" /> <script type="text/javascript">var toggle_cookie="xasset_co_uk_newbb16_G";</script> <script src="include/js/newbb_toggle.js" type="text/javascript"></script>
I must say that I am looking at Newbb 1.15. Could you specify which Newbb version you are looking at for reference?
Cheers.
McNaz.