This is due to the use of the adhesive on the display, in which for some devices is still in the process of setting. This means that give it a few days and the tint should go away. However if it doesn’t, don’t worry as your phone isn’t defective. It is possible that it could be a software thing and you can adjust it.
All you need is to fire up the Settings app, go to General, Accessibility, then Display Accommodations, Color Filters, and flip the switch to the ON position. After that as you can see in the screenshot to the right, you’ll be able to tweak the screen’s colors to your liking. To get rid of the yellow tint, just slide the Hue bar around until you achieve the color that you want.
Once you get it to the settings you like, you’re good to go. In a way you can check against a normal iPhone if you want to try and achieve the factory look. Complaints of yellow tints on display aren’t new and we have seen it happen in the past, but most of the time it is due to the adhesive and not so much a hardware defect.