The fix for this issue will be available in the next LIB version (2018.2.820). It will also be included in our official version – R3 2018, scheduled for the mid of September.
Project with a fix.
When you have a TextBlock Style that changes the Foreground and a GridViewCell Style also changing the Foreground, the GridViewCell one is not respected. Issue seems related to a Foreground binding in the ControlTemplate of the GridViewCell. A possible workaround is attached.