emacs does not honor my comment face customization

[Francis Moreau]

Hello,

I have the following in my emacs:

(custom-set-faces
  ;; custom-set-faces was added by Custom.
  ;; If you edit it by hand, you could mess it up, so be careful.
  ;; Your init file should contain only one such instance.
  ;; If there is more than one, they won't work right.
 '(font-lock-comment-delimiter-face ((t (:inherit font-lock-comment-face))))
 '(font-lock-comment-face ((((class color) (min-colors 8) (background light)) 
(:foreground "magenta" :slant italic))))
 '(font-lock-doc-face ((t (:inherit font-lock-comment-face))))
 '(font-lock-string-face ((((class color) (min-colors 8)) (:foreground 
"green")))))


and all work fine exept for the comment face customisation.

When editing a C source code, I need to reread my .emacs file to have
my comment face customization happens that is dispayed using the
"magenta" color.

Could anybody tell me why ?

thanks
-- 
Francis