As a result of research like this, I created
SunsetScreen to allow the user to change the screen's colour filter to *any* colour, not just a hue along the colour temperature scale. An orange tint is probably good at night for increased melatonin production, but a blue tint may be desirable during the day to increase seratonin.
I also prefer using it to Flux because you can set the exact time of sunset/sunrise instead of letting the seasons dictate it (4pm sunset in the winter? - thanks but I want the screen a normal colour at that time in the afternoon!).