Got iPhone 12 mini few weeks ago and compared to iPhone X (OLED) and Xr (IPS) I noticed that white balance is more accurate and TrueTone matches ambient light better. But sometimes I felt that 12 mini white/gray color is slightly off. I went to several Apple and 3rd party stores which had iPhones on display and compared visually to mine. All of them were about the same as mine with small variations in colors. Difference with previous iPhone models were much bigger than variations inside 12 model line. Also I compared 12 mini with calibrated Eizo display and noticed green tint on grey background. Eizo was set to 160cd/m² and iPhone was visually set to match brightness.
Today did measurements and can confirm in more scientific way my observations.
Measured iPhone 12 mini with DisplayCAL, i1 Display Pro and RGB OLED Samsung spectral correction. TrueTone and NightShift are both off. To achieve maximum brightness I turned off in Accessibility settings auto brightness. With auto brightness turned on maximum measured was 530cd/m², with turned off was 630cd/m². That can explain why display models in stores looks brighter than your personal devices. In Apple Store and most 3rd party stores display models have auto brightness turned off (I checked about about 20 devices in different stores).
TLDR: iPhone 12 mini display is very accurate between 250cd/m² and maximum brightness. DeltaE less than 1.0 considered as not visible to human eye. With brightness lower than 200cd/m² grey and white color get some green tint. White balance is calibrated very well and within range 6487-6529K (depends on brightness level).
iPhone X and Xr both looked more blueish compared to 12 mini, but 12 mini is more color accurate.
120cd/m²:
View attachment 1681567
135cd/m²:
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200cd/m²:
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235cd/m²:
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350cd/m²:
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400cd/m²:
View attachment 1681571
530cd/m² (max with auto brightness on):
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630cd/m² (max with auto brightness off):
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