Here it is, the grey css theme for the new UI integrated on master.
As seen with @aurelienpierre , I’ve worked on this theme and tested it with few users who makes some feedback.
The idea is to have an interface who reduce optic illusions that could add a dark or bright one about exposure. Having a grey theme as an alternative as the dark default one let the user choose.
For optic illusions about grey and shadows (so proximity of dark zones and the perception of colors), one of the best known experience is the checker shadows illusion from Adelson. See :
I’ve tried to propose the better compromise between reducing optic illusions, having a good contrast between elements of the interface, and having a good design. That was not so easy and had need some few hours to find that.