True Tone is a feature available on iPhones that uses advanced sensors to adjust the color and intensity of the display to match the ambient light, so that images appear more natural. It is on by default, but can be turned off in the settings. True Tone is intended to blend the screen into its surrounding environment, making it more comfortable to use by warming the screen as needed. It automatically balances the color temperature or how warm or cool it is on the iPhone with the surrounding environment. If you turn off True Tone, the display keeps color and intensity constant, regardless of changes in the ambient light. Some people prefer to turn off True Tone, while others find it helpful in reducing eye strain.