Could you quickly identify the open tab? I can't.
It is due to an update in the Zorin theme I suppose. If I use the "classic" appearance for Brave it is perfectly readable:
The Zorin Themes are solely under @AZorin and @zorink so tagging the ZorinGroup to review this issue.
As an aside: yes, the user can correct this in the theme .css file. But let's give priority to the ZorinGroup first, before supplying possible fixes here - this way the ZorinGroup can remedy it with an update affecting all users, not just the exclusive readers here.
In the Moderator forum, a thread is stickied exclusively for alerting the ZorinGroup for direct Zorin Issues. This is because the ZorinGroup cannot go reading the forum threads when they are tasked with developing the Operating System and their other projects like direct upgrade. So we set up a sticky that they can check for anything that needs attention. I linked this thread in that when I replied to you earlier.
Brave Browser, being a Chrome Browser deviation, would recognize the addressbar and tab bars for a system theme as the menubar class (generic) in the .css file.
We've just published a software update which makes the active tab colour different from the browser header's background to make it more visible, like so: