Wikimedia Bugzilla is closed!

resources/jquery.ui/themes/vector/jquery.ui.theme.css has a
 .ui-widget-content a { color: #362b36; }
which is hard to recognize as a link if you expect the usual blue. Additionally this overrides the red color for links with class .new, which is very bad when you want to provide a preview in a dialog.

Commons has a
/* Fix link color in jQuery dialogs */
.ui-dialog a {
 color: #0645AD!important;
}
in [[commons:MediaWiki:Common.css]], so I'm not the only one who dislikes this color. This makes links blue again, but still breaks preview of links to missing pages.

I suggest to just remove the line from jquery.ui.theme.css (for vector and for other skins as well).