Is these a way to change it so that Opus title bars don't change to white in the background? I might be missing the setting, but can't seem to find it.
My other Windows apps, like Explorer, change from the blue color I chose to a dark grey when they are not the active window.
The titlebars are drawn by Windows. Explorer has a non-standard titlebar, but if you compare to something like Notepad you should see the same thing.
I think the 1809 Windows update is meant to add an option to change the white inactive titlebar color, but I'm not sure as MS are still not rolling that out widely yet.
Oh wow. You're right. This is what happens when Directory Opus is the first thing I reinstall when I install Windows. With the custom Explorer titlebars I hadn't noticed yet. Hope that update comes out. Thanks!
Still waiting for usable toolbar-titlebar like browsers (e.g. Opera) and other apps have (e.g. Photoshop), where color is always styled by the app itself 
No browser has usable titlebars IMO. Chrome just forced out a new update which removed the option to keep the old style titlebar, and now you can't tell which window is active properly, or which tab is active within the window (depending on the settings you apply) if you also want Chrome to use the standard colors (rather than Blue = Active, Different Shade Of Blue = Inactive... blue is hardwired in my mind to mean the active window, since 1995, and that's what it means for all my other apps except the web browsers).
I tried every browser and they are all copying Chrome's bad ideas in that department. (Also Microsoft's, if you look at any of the Metro style apps, which are very hard to tell active from inactive, but it's easy to avoid using any of those outside of brief Windows settings changes.) I can't speak for the rest of the team but I absolutely hate this trend. (Although I am not against having alternatives as options for people who feel differently.)
I like it, more space.
I like the compactness, not needing an extra row for the tabs, but I hate the implementation in every browser now. More the colors than the layout, which is what this thread is about, I think.
Not sure how well tabs in the titlebar would work with Opus where you can have tabs on both left and right. You still need somewhere you can reliably use the drag the window around (which is also getting harder in a lot of browsers).
I've had a chosen inactive window title bar color for several iterations of Wndows 10. I think I used Winaero Tweaker to do it. Change color of inactive title bars in Windows 10 seems to be what Winaero Tweaker does under the covers.
(There are a few programs which now insist on coloring their own title bars without respecting system wide title bars, but most of them do respect those colors both active and inactive).
I used these instructions to make it dark: https://www.onmsft.com/how-to/how-to-get-dark-theme-title-bars-in-windows-10-without-changing-your-accent-colour
Alternatively, you can also use this tool: https://github.com/Superfly-Inc/Color-Changer/releases
For me, it works as it also keeps the accent color (For now).
EDIT: Coming back with an update on this, the accent color that I've set in the Settings app get forcefully applied after a while, so this isn't a solution after all.
In case anyone is still looking for a solution, I found one that works in Windows 10 21H1: How to get dark theme title bars in Windows 10, without changing your accent colour - OnMSFT.com
It requires adding a registry key 'AccessColorInactive' (DWORD 32-bit value) to HKEY_CURRENT_USER\SOFTWARE\Microsoft\Windows\DWM.
I use 434343 as the value.
