foo.el

(defun erc-highlight-nicknames ()
  "Searches for nicknames and highlights them. Uses the first                                                                                                                         
twelve digits of the MD5 message digest of the nickname as                                                                                                                            
color (#rrrrggggbbbb)."
  (with-syntax-table erc-button-syntax-table
    (let (bounds word color new-nick-face)
      (goto-char (point-min))
      (while (re-search-forward "\\w+" nil t)
        (setq bounds (bounds-of-thing-at-point 'word))
        (setq word (buffer-substring-no-properties
                    (car bounds) (cdr bounds)))
        (when (or (and erc-channel-users (erc-get-channel-user word))
                  (and (not erc-channel-users) (erc-get-server-user word)))
          (setq new-nick-face (gethash word erc-highlight-face-table))
          (unless new-nick-face
            (setq color (concat "#" (substring (md5 (downcase word)) 0 12)))
            (if (equal (cdr (assoc 'background-mode (frame-parameters))) 'dark)
                ;; if too dark for background                                                                                                                                         
                (when (< (hexcolor-luminance color) 85)
                  (setq color (invert-color color)))
              ;; if to bright for background                                                                                                                                          
              (when (> (hexcolor-luminance color) 170)
                (setq color (invert-color color))))
            (setq new-nick-face (make-symbol (concat "erc-highlight-nick-" word "-face")))
            (copy-face 'erc-highlight-nick-base-face new-nick-face)
            (set-face-foreground new-nick-face color)
            (puthash word new-nick-face erc-highlight-face-table))
          (erc-button-add-face (car bounds) (cdr bounds) new-nick-face))))))