Comment by fsh

I believe this is more folklore than science. A significant color shift happens only for a couple of minutes during sunrise and sunset. The change in brightness is probably significant, but it is hard to believe that the color has a significant physiological effect (but the placebo could be very strong!). In my experience, f.lux and co. make it pretty difficult to read text due to the low contrast, and simply changing the screen brightness is much more effective.