Selected tab group is hard to spot
With the new color scheme, it's hard to spot which tab group is selected. See the screenshot. Perhaps lighten the selected tab group rather than darken it. That's the usual color scheme used elsewhere. Other tabs are usually darkened, while the currently selected one is lightened, to bring focus to it.

It could use some fine-tuning, sure. But you also have the arrow below it, should make it much easier to spot than highlight colors ever could. ;)
Honestly I didn't even notice the arrow initially. Different colors definitely make a bigger difference than symbols.
I guess that highlighting the selected group would cause conflict with the white arrow (less contrast). I use always the arrow to detect the current group and it works fine for me.