gurjyot XxPoNaGeXx no, it's not done just yet. I have also heard from Toby that it will be in core but around 0.3 version and not before.
Pollux Razor I think he just want to change colors of elements, and what Pollux said is something that he do not need to do and can achieve with few lines of custom css. The idea of using global variables was brought up by 0E800 and Frink wanted to turn this into an extension. That's why I connected the question raised here with his plan described there just 18 hours earlier.
clarkwinkelmann freelook the extension was actually released shortly after the last message of this thread one year ago https://discuss.flarum.org/d/11134-night-mode-by-reflar