The colour of tabs in combine mode is never controlled by the custom tab colours and never has been.  The menu that lets you pick the colours says colours only apply to always place above mode.

The tab colour should be based on your OS settings with active tabs being white typically unless dark mode is enabled and you are using a dark mode aware app.

Are you able to provide a screenshot showing the issue?  Black would suggest you have your OS set to Dark mode?

Hello,
Sorry to hear you are having issues. That blue (1,28,130) somehow make the groupy tabs turn black with White text. Adjust the color a little and it will change to white tabs with black text. My guess it has to do with Windows Accent colors.

Basj,
Stardock Community Assistant.

We should have this addressed in v1.4 when it is released.