Everything indicates that the dark state is at an early stage of development, as it may not be applicable to the page, but is available in some platform groups. According to all of Android 4, some users have even seen it on the menu with a translucent black color.
It's not yet clear if the platform will use black as a staple for this design, in some photos you can also see the gray color they are testing. However, the most likely thing is that Facebook opts for Black because in messenger dark mode it's color, they mentioned the same medium.
By "early stages of development", this is what I mean
At this time only the tabs of the groups look good for the demo ? pic.twitter.com/L1SHaWlSk1
– Jane Manchan Wong (@wongmjen) August 13, 2019
Remember that this year Facebook introduced its new design as FB5, which was characterized by its bright white interface, which according to Rang, has received numerous complaints that it may hurt some users' views at night because of its power.
It is still unclear when this new tool will launch, as each platform takes different time to develop details of its new functions. For now, it's just a matter of paying attention to the information that the company distributes on its official website.