NewAdwaita: change color scheme from warm to neutral
New Adwaita theme is warm. It is important to save neutrality of GUI for photo and video editors, image viewers and video players: if window titles\headerbars and backgrounds will have some warm\cold tone it will be less comfort for content creators and peoples who sees difference.
Almost grey but not exactly grey background will confuse WB detection built inside users brain. Brain will treat warm grey (#f6f5f4) as neutral grey (#f6f6f6). Background should be or neutral or more coloured.
Adwaita as default GTK theme should stay more neutral.
Visual difference between current NewAdwaita and my proposal (proposal at the bottom of images):
Same thing with NewAdwaita dark.
I changed saturation (in HSV) for backgrounds and gradients from "near zero" to zero in Adwaita updated theme: NewAdwaitaNeutral.tar.xz