On and do as below. Credit from another MacRumors member but I can’t find the original thread now.
“Thought my screen tone is just way too warm when I started using the phone, so did some adjustment to make it more natural.
Go to Settings->General-> Accessibility ->Display Accommodation->Color Filter-> Switch to ON->Check Color Tint-> Scroll Intensity & Hue all the way to the right ->Adjust Hue to the left so that the screen color from Red to Purple-ish (Towards Blue). Once you determine the sweet point, scroll intensity all the way to the left. Now you should have a much better display tone.”