"unread" thread in a different color?

[David S Goldberg <david.goldberg6@verizon.net>]

Probably a feature request but perhaps there's something I could do on
a hook.  I have a couple of groups on which I set the display
parameter to t resulting in large summary buffers with a lot of O and
! marked articles.  To deal with the large numbers I hide all threads
by setting gnus-thread-hide-subtree to t by default.  The problem with
this is that when I have more than one unread article in the group it
is not clear in which threads I have unread messages (except the first
because that one always seems to be unhidden automatically).  I've got
the summary sorted by thread with most recent number and then by most
recent date.  This helps, but it's still not everything I would like
because, for example, while I might know that there are four unread
messages in the summary, it's not clear whether they are all under the
first thread or whether there is one under each, or some combination.
What I'd like is some way to have a thread with unread messages in it
shown in a different color.  I've already given up on having an unread
count in the summary line.  I wrote a function that counts the number
of unread messages in the thread below the current summary line:

(defun dsg-unread-in-thread ()
  (length
   (remove nil
	   (mapcar
	    'gnus-summary-article-unread-p
	    (gnus-summary-articles-in-thread)))))

But as that changes (e.g. by reading an article), there doesn't seem
to be an easy way to update the parent summary lines.  My hope was
that it wouldn't be that hard to incorporate into
gnus-summary-highlight since then I'd only have to compare against 0
and not worry about maintaining counts.  Is there any way to do
something like that?

Thanks,
-- 
Dave Goldberg
david.goldberg6@verizon.net