I can't stand this sort of functionality, whenever I look at red-shifted dimmed display it makes me feel like I'm going blind! I know the bad things blue light does to the human body, especially late at night — but for me limiting screen time (with full colour) is still preferable to looking at a red screen.
However, I do like the Flux team a lot better than Apple :P If I had to pick one to suppose I'd want to support Flux.