The following devices feature True Tone technology:
iPhone X
iPhone 8
iPhone 8 Plus
iPad Pro 12.9-inch (second generation)
iPad Pro (10.5-inch)
iPad Pro (9.7-inch)
How to control True Tone from iOS 11 Control Center
To adjust display color temperature of your device on the fly, use Control Center to toggle True Tone:
1) Swipe up from the bottom edge of your iPhone to pull up Control Center. On iPads, swipe up from the bottom in any app (it doesn’t work on the Home screen) or simply double-click the Home button.
2) Now press the brightness bar with 3D Touch. On non-3D Touch hardware, tap and hold the bar.
3) Tap True Tone below the slider to toggle the feature quickly on or off.
TIP: You can also toggle Night Shift on or off from there.
Like before, you can enable or disable True Tone in Settings → Display & Brightness. Keep in mind that vision accessibility features such as Invert Colors, Smart Invert, Grayscale and Increase Contrast might turn True Tone off.
Should you leave True Tone on all the time? That depends on your eyesight, lighting and environment.