I've read the multifile and parsing sections of the AUCTeX manual but I still can't seem to figure this out. I expect that this is a common problem but I can't seem to get AUCTeX to recognize natbib (or another other package) commands in terms of highlighting in any other file than the master file. I've added the following to my emacs file:
(setq TeX-auto-save t)
(setq TeX-parse-self t)
(setq-default TeX-master nil)
;; colour highlighting
(global-font-lock-mode t)
(setq font-lock-maximum-decoration t)
;; use reftex
; with AUCTeX LaTeX mode
(add-hook 'LaTeX-mode-hook 'turn-on-reftex)
; with Emacs latex mode
(add-hook 'latex-mode-hook 'turn-on-reftex)
; use natural science bibliography style
(setq reftex-cite-format 'natbib)
This works well for the master file but not for any of the other files that make up the entire document. This is what I have at the end of each of my sub-files: