Regarding dark theme the dark app background is 12.5% gray and the lighter offset backgrounds are 17.5% gray. If it appears pitch black it's not because the theme is made for OLEDs rather your displays are miscalibrated and completely crushing blacks. If you enable transparency effects the color of your background will blend with these and raise/lower them accordingly.
Hmm, are you sure about this? From a quick search, I'm able to find plenty of people complaining about the dark background being pitch black[0] (there's also a Feedback Hub item linked in there, not able to open it as I'm on Linux). I might be wrong, but I am fairly sure my display is not mis-calibrated, as I actually spent a lot of time calibrating it when it got here (have only had it a handful of months). The only downside of the monitor is that blacks really smear when you move them around, whereas dark greys are substantially better.
That's one of the reasons I really dislike the pitch black mode, anyway. It also just looks horrible on anything that isn't AMOLED, IMO.
> If you enable transparency effects the color of your background will blend with these and raise/lower them accordingly.
That's only for surfaces with blur enabled though, like the sidebar in Settings or the taskbar. Non-blurred surfaces are pitch black.
[0]: https://old.reddit.com/r/Windows10/comments/6nzs34/any_way_t...
As much as I'd like to be able to claim to be a color expert that can eyeball HSL values with enough certainty to give the answer in decimal percentages the above numbers are from color picker readings of a screenshot of my install.
> I'm able to find plenty of people complaining about the dark background being pitch black[0]
I can't speak about what was true 4 years ago in a preview build adding dark theme, or Windows 10 at all for that matter as I don't have a current install anymore, but for Windows 11 today the above are the measured values.
> That's only for surfaces with blur enabled though, like the sidebar in Settings or the taskbar. Non-blurred surfaces are pitch black.
For that particular preview version of 10 perhaps, in Windows 11 there is also a new opaque material called Mica used heavily throughout the interface as it has less of a performance hit (no blur/transparency) https://docs.microsoft.com/en-us/windows/apps/design/style/m...