I use the BLACK theme.
Since Android PIE the navigation bar can change the color and use the app color.
In fasthub the navigation bar becomes black with the white buttons.
Sometimes even the buttons become black, so there is only a "invisible" navigation bar.
The buttons are still usable.
FastHub Version: 4.6.7 Enterprise Premium Everything unlocked Android Version: 9.0 Device Information: Sony Xperia XZ2
MODEL: XZ2
I use the BLACK theme. Since Android PIE the navigation bar can change the color and use the app color. In fasthub the navigation bar becomes black with the white buttons. Sometimes even the buttons become black, so there is only a "invisible" navigation bar. The buttons are still usable.