Brave supports it’s own style (‘Classic’) or it can use the GTK (‘GTK+’) style. Unlike Firefox, Brave does not support native-looking window controls when not using the native titlebar though.
In order to make Brave feel more integrated, it is possible to set the titlebar color scheme to the same colors Brave uses (on KDE at least) when using the ‘Classic’ Theme.
Allow a setting next to the ‘Brave Colors’ theme settings that makes brave always use the same colors, even if it’s not the top most window. This would prevent it from turning a darkish grey and always stay black
Why it should be implemented
Presumably really easily implemented, and would go a long way towards making Brave feel more integrated on KDE (and possibly other desktops (I cannot speak for them as I do not use them)).
This is what the browser looks like when active. As you can see the titlebar nicely blends in with the rest of the browser UI.
Meanwhile this is what the browser looks like when not the active window.