With its latest iOS 9.3 beta, Apple is for the first time allowing users to access and control display temperature on their iPhones and iPads, albeit in limited fashion, through a feature called Night Shift.
According to Apple, the cleverly named Night Shift shifts an iOS device's display color temperature to help ease physiological side effects of being exposed to cool blue light — a default temperature for most LCDs — at night.
When activated, Night Shift uses the device clock and geolocation tools to calculate local sunset, automatically shifting display colors toward the warmer end of the spectrum for optimal night time viewing. Colors return to normal in the morning.
In iOS 9.3, Night Shift is found in the Display & Brightness settings menu under "Blue Light Reduction," and comes toggled off by default. Users can dynamically preview cool and warm tones via a slider control, though an exhibited setting will only by applied when Blue Light Reduction is switched on.
In practice, the slider's midpoint is not actually the factory iOS device setting. Sliding all the way to the "Cooler" end of the spectrum reproduces a normal operating color temperature, while the slider midpoint is halfway between that and Cooler's extreme "Warmer" opposite.
For those familiar with the Kelvin-based color temperature index, Apple's warmest setting appears to border on a CCT of 2,700K, normally associated with warm white LEDs. A good real world example is a deep yellow-orange or ochre sky at sunrise or sunset.
There are few customizations offered with Night Shift, though users can schedule their device to make color changes from sunset to sunrise or create custom schedule, perhaps just before before bed to sunrise.