New UI: use system colours for title bar

Is there any setting I'm missing to use system colours in title bar? Right now, it's dark grey for active window and lighter dark grey for inactive window, which is not only very different from my OS settings but quite an accessibility issue, esp. with multi-monitor setups.

I've enabled “Show main menu in a separate toolbar” to save one click when using menu items and I run PhpStorm both in Windows 10 Home and KDE Plasma 5.