Well, blue light is a thing and I heard it can cause severe long-term issues. It emits far more energy having a shorter wavelength. What are some ways to prevent this? You can actually set your Lumia to warmer sets as I stated in a different thread. Again, you go to Settings>Extras>Colour profile> click the drop down menu and select Advanced, then set it to a warmer colour temperature. On IOS 10 it should be automatic, but you can customize it by going to Settings> Display & Brightness> Night Shift.