As additional information for everyone; yes you can tweak/play about with the colour filter options deep within the settings.
Settings > Accessibility > Display & Text Size > Colour Filters [switch "On"] > Colour Tint
... then adjust Intensity and Hue to a point where you feel it is as close to a neutral white as you think is possible
You will likely find that the "Intensity" slider produces a result that is ridiculously overkill (not an understatement) and thus will find you'll probably have to adjust this fully to the minimum point (fully left). After that you'll move on to the "Hue" slider and will have to adjust this as mentioned above until you find a point that you consider to be as dead neutral white as you think is possible, or at least to your best likening.
However the Problems: -
- You cannot get it to a dead neutral white that is completely devoid of any colour hue/tint whatsoever. The closest you may get, is for a more cool white which has an undeniable blueish hue/tint. It's not by any means a neutral white and this can be seen when putting it next to a true white display, which in my case can be seen when comparing next to my older iPhone XS which has such a neutral white, that it's like eye candy as it blends in amongst all the other colours in a picture. Even my cheaper and now ageing 42inch LED TV has a balanced white.
- When you do find this cool-white spot on the Hue slider, there is sadly a trade-off. This trade-off may not be a problem to some, however for me it's just to big. You lose slight brightness power output. The iPhone 12 Pro Max does have some good, even great features and for me one of the most rewarding, satisfying improvement that I was very happy with was the increased brightness power output which always helps to make a phone easier to see in bright environments and Sunny days. However this is slightly affected with the Colour Filter enabled.
- Quite simply, we shouldn't have to take these desperate measures as the iPhone 12 Pro Max should have been designed, calibrated and manufactured with a truly state of the art display (especially with the 1,399 price tag).
If your happy with a slight blueish hue/tint for a much cooler white display (too much in my opinion) and you don't mind taking a knock with a trade-off with slightly reduced overall brightness power output, then you maybe fine with it and if you are then I've inserted a screen capture below of what I found and think is the sweet spot for that. Remember it's a screen capture and not a photo, so does not reflect the real screen's actual tint as it's purely for the adjustment settings only. I hope it may help some, however personally I value brightness power output to much and therefore not prepared to suffer the trade-off.
(screen capture - not photo)