Available in: Tools->Options->Application colors

Change-Id: I6e4f7a0dcad9a6ee222275019596853f0cbd3ab0
Reviewed-on: https://gerrit.libreoffice.org/51791Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Szymon Kłos <szymon.klos@collabora.com>
Reviewed-on: https://gerrit.libreoffice.org/51976Reviewed-by: Andras Timar <andras.timar@collabora.com>
Tested-by: Andras Timar <andras.timar@collabora.com>