Hi Jacob,
If you want to separately configure the Header Band background color of that DW in Theme.json, it is not supported. You can refer to the PB help in the link below:
“The color of the DataWindow band (except for the Header of Grid and Crosstab DataWindows) is not configurable in the theme file; it is determined by the settings in the painter.”
https://docs.appeon.com/pb2019r3/pbug/ch02s01.html#Understanding_what_can_and_cannot_be_set_by_the_theme
This design is to retain the user’s specific color settings.
If you want the Header band color the same as the DW background color, I suggest you set the background color of the Header Band to transparent color in DataWindow.
Regards,
Ken