[O] How to change color of (part of) agenda header

[Sebastien Vauban]

Hello,

I'm trying to get part of the agenda header in another color, here
"TODAY":

--8<---------------cut here---------------start------------->8---
  (add-to-list 'org-agenda-custom-commands
               `("f" "Today"
                 (;; list of all TODO entries with deadline today
                  (tags-todo "DEADLINE=\"<+0d>\""
                             ((org-agenda-overriding-header
                               (concat "DUE " #("TODAY" 0 4 (face (:foreground 
"red")))))
                              (org-agenda-skip-function
                               '(org-agenda-skip-entry-if 'notdeadline)))))
                 ((org-agenda-format-date ""))) t)
--8<---------------cut here---------------end--------------->8---

The goal is to make what's unique and different from the next agenda
blocks very outstanding.

Though, it does not work: text is simply copied, as if text properties
did not exist.

Am I missing something, or writing it in a buggy way?

Best regards,
  Seb

PS- I tried strings with `propertize' as well, with no more success.

-- 
Sebastien Vauban