Change the colour of tabs

[HanVroon]

Hello,

I thought it was possible to change default colours . I use the Default theme.
I red about stylesheets (*.qss files).
I have a style_sheet.qss and a style_sheet_win.qss in my profile.

I would like the colour of the active tab (for one file open) to be more different in colour that the oter tabs.
I can sometimes hardly see which tab is active.

I randomly tried changing values at several QTabBar::tab: entries, but nothing happens.
How do I change the background colour of the active tab?

Regards,
Han

[HanVroon]

Additional question:
There is a default file (I think):
C:\Program Files\XnViewMP\UI\style_sheet.qss

And the same file is in my profile directory (databases path).
To test I modified lots of colour values to see if anything changed, but XnView MP looks the same as before (with the default theme).
Does anyone know (and want to explain) how these stylesheets work?

[HanVroon]

Never mind, after a lot of fiddling I found out how it works.