Unfortunately, also all bars are coloured and my theme is overruled.

I think you should confine yourself to the tabs only or build in a feat to adjust whether one also wants to change the bar colours and/or theme. Also only the current tab is coloured. the rest is hardly visible against the background.
So disabled it, unfortunately.

But I realize that FF57 causes you a lot of work and is restricted in how you may adjust feats like tabs.