Note that the mockup in the previous comment was made by splicing in the non-focused state of the Tree Browser for the two upper-level pages (parent pages). So support for this colour combination already exists in GTK (in the non-focused state).
Note that the mockup in the previous comment was made by splicing in the non-focused state of the Tree Browser for the two upper-level pages (parent pages). So support for this colour combination already exists in GTK (in the non-focused state).