Couple of points for the doubters
This isn't a hypothetical idea. The earth changes from blue to yellow every dawn and every dusk
Our bodies are already configured to read the signals and adjust our sleep pattern to take advantage of them
Daylight beginning in the morning is blue. Our eyes adjust (again, twice per day), so we believe we're looking at white.
Running blue/daytime colors after sunset tricks your brain into thinking it's perpetual morning and that you should be wide awake. think: caffeine
If your body is used to running blue light after sunset, you can't just go full yellow. The feature has a slider because you need to gradually adjust
Start with the slider on the left, and move it one notch over every day or two. After a week or two even the far right shouldn't feel off
Once your eyes are trained to prefer the natural warm color after sunset, blue will appear harsh
This isn't all or nothing. Just like caffeine, blue light can be used when and where you want it. Need to cram for a test or finish a presentation, leave the blue cranked up
Our homes are filled with artificial light. If you have other lighting that is daytime/blue, this by itself will not be enough. To see if your Apple devices are keeping you up, you also need to turn off fluorescent and LED bulbs