Check out "Darker Reader" extension... now you'll get that everywhere, automatically, with good looking dark colors.
I think it achieves that by leveraging color theory and CSS filters.
Once you try it you cannot go back :)
I am not involved in development nor devs are friends of mine, I just think it didn't get all the exposure it deserves.
PS if you're on chrome, after installing Darker Reader the infamous chrome white flash problem will mess with your eyes... Following thread has a partial solution to that: