Color of Top bar

tistou 

Maybe, I mixing up jargon or terms are confusing this... The pic I showed was browser windows... and then there are, also, app windows.  Again, the browser title bar colour CAN be set & is determined by what OS Accent colour is used & if show on title bars is selected.  Anyway, here is another shot near what you described with an IE window front & centre, a couple of Edge C windows behind and a Pictures 'folder' window & the Mail app.  It's not restricted to blue & black.  Nor as you see does THE colour change except for its intensity (on the browser windows). The pics window & Mail are dark because the OS is set to Dark.  I don't know if any of this speaks to your concern or not, but, trying, at least.

Pretty funky clock, too, eh? 

Cheers,
Drew