This does Just Work™ for me if I remove the two spaces at the front of each line. I never use the indentation, so I am not sure what the interplay there is.

John

-----------------------------------
Professor John Kitchin 
Doherty Hall A207F
Department of Chemical Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
412-268-7803

On Wed, Aug 22, 2018 at 4:51 AM, Marcin Borkowski <mbork@mbork.pl> wrote:
Hi all,

I hoped this:

#+begin_src diff
  @@ -1,5 +1,5 @@
  -lorem
  +Lorem
   ipsum
   dolor
   sit
  -amet
  +amet.
#+end_src

would Just Work™, i.e., the diff would be font-locked like in
diff-mode.  Well, it is not.  How do I convince Org-mode to color my
diffs?

Best,

--
Marcin Borkowski
http://mbork.pl