I looked with firefox inspector and for some reason in your old index the empty category has the same class as the category with files: .catrow_noalb. Maybe you have function $template_cat_list in themes/your_theme/theme.php and you edit it. You can find the original function in themes/sample/theme.php or maybe you edit the function $template_cat_list in include/themes.inc.php in your previous coppermine (the upgrgade replace it with the new themes.inc.php). You should never edit themes.inc.php. You can find all the functions in themes/sample/theme.php. Just copy in themes/your_theme/theme.php only the functions you need to edit.
Or maybe your old index.php has .catrow_noalb class for all categories (empty and with files).
With the new index the empty category has class .catrow_noalb and the category with files has class .catrow. This is how it should be in cpg 1.5 .
Solution: in your style.css you have:
.catrow_noalb {
background: #727070 ;
color : #c3c3c3;
-moz-border-radius: 5px;
border-radius: 5px;
-webkit-border-radius: 5px;
-webkit-transition: all 0.2s ease-in;
-moz-transition: all 0.2s ease-in;
-o-transition: all 0.2s ease-in;
padding-top: 3px;
padding-right: 10px;
padding-bottom: 3px;
padding-left: 10px;
border-bottom: 1px solid #1a1a1a;
}
.catrow {
background: #252525 ;
padding-top: 3px;
padding-right: 10px;
padding-bottom: 3px;
padding-left: 10px;
-moz-border-radius: 5px;
border-bottom: 1px solid #1a1a1a;
border-radius: 5px;
-webkit-border-radius: 5px;
-webkit-transition: all 0.2s ease-in;
-moz-transition: all 0.2s ease-in;
-o-transition: all 0.2s ease-in;
border-bottom: 1px solid #1a1a1a;
}
In class .catrow change background: #252525 ; with :
background: #727070 ;
color : #c3c3c3;
If you don't want the files and album count read this thread to learn how to edit $template_cat_list function:
http://forum.coppermine-gallery.net/index.php/topic,77917.0.html