I just purchased an iPhone 11 Pro, and I noticed the screen has a yellow tint color. I was previously using an iPhone X. On both phones "True Tone" was off, but the screen color on the iPhone 11 Pro had a yellower tint. I put the iPhone X and the iPhone 11 Pro side by side, and it made the yellow tint more noticeable. As you can see from the image above, the iPhone 11 Pro has a yellower tone than the iPhone X. To the naked eye, it's a lot more noticeable than the image above. Fortunately, you can make adjustments to the screen to remove the yellow tint. The directions below are for iOS13, but iOS 12 or lower should be similar.

The first thing you need to do is turn off "True Tone" by following the instructions below:

Go to Settings > Display & Brightness

Tap "True Tone" to off

The next thing to do is to change the "Color Filters" to the desired color by following these instructions:

Go to Settings > Accessibility > Display & Text Size > Color Filters

Tap "Color Filters"

Tap "Color Tint" so it's checked

Slide the "Intensity" all the way to the left

Slide the "Hue" to about 75%

I would recommend playing with the hue until you find a color that you like. I think it would be challenging to get precisely the color that was on your old iPhone, but you can get the screen to look cooler rather than warmer and yellowish. After you find the screen color you desire, I would recommend using the phone for a day to see how you like it. Although the screen color may not be the same as your previous iPhone, you will find that your eyes adjust to things. I found an adjustment that made my iPhone 11 Pro look "cooler," and now after putting my iPhone X side by side with my iPhone 11 Pro, the iPhone X appears to have a slight yellow tint compared to my iPhone 11.

After doing a little research, I noticed complaints about the yellow tinted screen as far back as iPhone 7. Though most of the complaints I found were on iPhone Xs, iPhone Xs Max, iPhone 11, iPhone 11 Pro, and iPhone 11 Pro Max.

As you can see from the image below, the iPhone X has a yellow tint while the iPhone 11 Pro, with Color Tint adjusted, removed most of the yellow tint.

For those curious about the Color Filter settings that I used, see the image below. The intensity was all the way to the left and the Hue is at about 75%. I would recommend playing with it until you get the screen tint you desire.