On Saturday, 17 Jun 2017 at 02:34, edgar@openmail.cc wrote:

[...]

> Thanks, Eric. Unfortunately, that did not work. It does change the 
> background and foreground colors, but the \tensor symbol is now 
> "invisible" (it is black, and the background is also black). The rest of 
> the equation looks fine.

Strange.  Maybe post an ECM for others to experiment with?
-- 
: Eric S Fraga via Emacs 26.0.50, Org release_9.0.6-425-gf4fca1