you can add a rule like this in an org-mode hook:

#+BEGIN_SRC emacs-lisp :results silent
(font-lock-add-keywords
 nil
 '(("^-\\{5,\\}"  0 '(:foreground "red" :weight bold))))
#+END_SRC

that will make a line starting with at least 5 - be red and bold in color.

John

-----------------------------------
Professor John Kitchin (he/him/his)
Doherty Hall A207F
Department of Chemical Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
412-268-7803
@johnkitchin
http://kitchingroup.cheme.cmu.edu



On Tue, Sep 28, 2021 at 4:00 AM Eric S Fraga <e.fraga@ucl.ac.uk> wrote:

> You could use hi-lock-mode to define your own colouring for such
> lines.  But I'm sure those that under font-locking better might be able
> to add appropriate rules for this horizontal line construct.
>
> --
> : Eric S Fraga via Emacs 28.0.50, Org 9.5-g9a4a24
> : Latest paper written in org: https://arxiv.org/abs/2106.05096
>
>