Emacs font lock mode: provide a custom color instead of a face

On this page discussing font开发者_StackOverflow lock mode, an example is provided which highlights a custom pattern:

 (add-hook 'c-mode-hook
           (lambda ()
            (font-lock-add-keywords nil
             '(("\\<\\(FIXME\\):" 1 font-lock-warning-face t)))))

Is there a way to provide a custom color instead of font-lock-warning-face and without defining a new custom face. I want to be able to write something like:

(font-lock-add-keywords nil '(("\\<\\(FIXME\\):" 1 "Blue" t)))

or an RGB color definition:

(font-lock-add-keywords nil '(("\\<\\(FIXME\\):" 1 "#F0F0F0" t)))

Using the double quotes doesn't work. Do you know what will make it work?

(font-lock-add-keywords nil '(("\\<\\(FIXME\\):" 1 '(:foreground "blue") t)))
(font-lock-add-keywords nil '(("\\<\\(FIXME\\):" 1 '(:foreground "#F0F0F0") t)))

A full list of attributes is in the manual.