in my iphone 8plus truetone is in active, now what i should to do to activate the truetone

Hi nisar84,

In Settings > Accessibility > Display & Text Size, do you currently have any of the color options enabled? (Increase Contrast, Smart Invert, Classic Invert, Grayscale, Color Filters)

If any of these settings are turned on, it may remove the True Tone option. If anything is enabled on that page, turn it off then navigate back to Settings > Display & Brightness, and see if the True Tone option is available.

Also, be aware that any replacement to your device screen not done by Apple or an Apple Authorised Service Provider disables TrueTone.

Go to the control centre click long on the brightness changer than click on the activate button.

Have you tried to turn it on in the settings in the display settings?

Has your display ever been replaced?