Change the color of article counts when equal to 0

[Sébastien Vauban]

Hello,

I'm using 4 count numbers on every group line:

--8<---------------cut here---------------start------------->8---
      ;; format of the group buffer
      (setq gnus-group-line-format (concat "%M%m%P "
                                           "%(%-39,39g%) "
                                           "%5{%3y Unread%} "
                                           "%6{(%3U Unseen)%} + "
                                           "%7{%3T Ticked%} < "
                                           "%6t Total Items"
                                           "\n"))
--8<---------------cut here---------------end--------------->8---

with these fonts:

--8<---------------cut here---------------start------------->8---
      ;; create faces for article counts
      (defface my/unread-face
        '((t (:weight bold :foreground "black"))) "Ticked group face")
      (defface my/unseen-face
        '((t (:weight bold :foreground "blue"))) "Ticked group face")
      (defface my/ticked-face
        '((t (:weight bold :foreground "orange"))) "Ticked group face")

      (setq gnus-face-5 'my/unread-face)
      (setq gnus-face-6 'my/unseen-face)
      (setq gnus-face-7 'my/ticked-face)
--8<---------------cut here---------------end--------------->8---

I would like to see the numbers in very light gray when they're equal to 0,
but can't figure out how -- or, even, if possible at all... Can you help me?

Best regards,
  Seb

-- 
Sébastien Vauban