I want to show @ symbols (meaning dereference) in red in clojure-mode. How do I do that?
Based on the examples in section Customizing Search-Based Fontification of the elisp manual, I would propose this:
(add-hook 'clojure-mode-hook (lambda () (font-lock-add-keywords nil '(("\\(@\\)" 1 '(:foreground "red") prepend)))))
This uses an anonymous face with red foreground, any face could of course be used.