It can be fixed actually pretty easy. I bet that the true tone isn’t working either. [br]
In order to avoid the problem, the technician should be able to copy the chip ID of the old display and transferred to the new display via a programmer computer. Type in google images “truetone fix”, and you will see it. Same programmer you can use it for camera replacing, battery and other things, by doing the exactly same thing. [br]
Another thing is that the service should use only the OEM OLED displays that have the truetone chip builtin. [br]
Be careful these days as many services are hiring 2nd hand technicians, and they would lie to you, and mount just an regular LCD display. [br]
Your welcome,
just an old school technician