why not showing true tone on phone

Hi mir135,

Thank you for participating in the Apple Support Communities. We understand your device does not have the True Tone option in Settings > Display & Brightness, and we'd like to assist.

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.

Adjust the brightness on your iPhone, iPad, or iPod touch

We hope this helps.

Take care.

Have you replaced the screen? If yes was it done by Apple or one of it authorised service providers?