Hi Sudarak,
If there seems to be a persistent yellowish tint to the iPhone, it may be the True Tone feature. Depending on the ambient lighting, it will adjust the color temperature of the iPhone to match for an easier viewing experience.
You can see info on True Tone here:
"Adjust brightness and color temperature in Settings
- In the Settings app, tap Display & Brightness.
- Drag the slider to the right or left to adjust the brightness.

From here, you can turn on Dark Mode, which is designed to make the screen easier on your eyes. Dark Mode uses a dark color scheme that works system wide, including with the apps that come with your device and with many third-party apps.
True Tone,* which is on by default, uses advanced sensors to adjust the color and intensity of your display to match the ambient light, so that images appear more natural.
If you turn off True Tone, the display keeps color and intensity constant, regardless of changes in the ambient light.
You can also turn on Night Shift, which adjusts the colors of your display to the warmer end of the spectrum and makes the display easier on your eyes. To adjust the color temperature to be warmer or colder, go to Settings > Display & Brightness > Night Shift and use the color-temperature slider."
If the issue persists or the display continues to flicker, we'd advise contacting Apple Support. The iPhone may need to be inspected.
Take care.