LaTeX org-mode tikz with a dark background plots with black on black

[Vladimir Nikishkin <lockywolf@gmail.com>]

Hello, everyone

I am trying to follow the example from the contributed manual:

https://orgmode.org/worg/org-contrib/babel/languages/ob-doc-LaTeX.html#org30df2de

The code I am trying to get compiled is the following:

#+header: :imagemagick yes :iminoptions -density 600 :imoutoptions -geometry 200
#+header: :fit yes :headers '("\\usepackage{tikz}")
#+header: :buffer on
#+begin_src latex :results raw file :exports code :file test.png
  \usetikzlibrary{trees}
  \begin{tikzpicture}
    \node [circle, draw, fill=red!20] at (0,0) {1}
      child { node [circle, draw, fill=blue!30] {2}
      child { node [circle, draw, fill=green!30] {3} }
      child { node [circle, draw, fill=yellow!30] {4} }};
  \end{tikzpicture}
#+end_src

I am getting the picture, and the circles are where they should be,
but (!), the arrows are black, which makes them not really visible on
a black background. How would I either make the background white, or
(better) just make the foreground white (just for this particular
block of latex, not for export, and not even for the entire file).

The formulate like \( e = mc^2 \) are properly rendered both in Emacs
(white on black), and when exported (black on white).

Any suggestions welcome.



-- 
Yours sincerely, Vladimir Nikishkin