Comment 9 for bug 1527053

This is not a dark theme/light theme issue. Both Ubuntu's dark theme Ambiance and light theme Radiance have the same issue. In Debian Jessie, when you use the tweak-tool to change to a dark theme, it correctly changes the tab color in LibreOffice.

Another difference between Debian's Dark theme and Ubuntu's, is that the dark them in Debian also changes the sidebar. However unlike the tabs, the sidebar uses the correct uses black text.

Maxim or Björn,
It seems that Ubuntu's theme information is incomplete. Should a launchpad bug be filed? In any case, we need to emulate the sidebar's fall-back behavior. If you can't read the background color, don't change the font color.