Emacs AucTex Latex syntax prevents monospaced font

For the specific example of sections, chapters, etc., add the following to your .emacs:

(setq font-latex-fontify-sectioning 'color)

Edit Here is the config I usually use to customise the AUCTeX formatting:

;; Only change sectioning colour
(setq font-latex-fontify-sectioning 'color)
;; super-/sub-script on baseline
(setq font-latex-script-display (quote (nil)))
;; Do not change super-/sub-script font
(custom-set-faces
 '(font-latex-subscript-face ((t nil)))
 '(font-latex-superscript-face ((t nil)))
 )
;; Exclude bold/italic from keywords
(setq font-latex-deactivated-keyword-classes
    '("italic-command" "bold-command" "italic-declaration" "bold-declaration"))