Hi @HattieLovesSalsa, I understand that this is a very neat feature and can be very helpful, however it's not available in the Xperia XZ Premium. I have not used an application that will add this kind of effect myself, so I can't recommend any specific application, but it's always recommended to check the reviews that other users has left for a certain application, and I also very often check how many downloads an application has, as this will tell me if a lot of users are using it and there is in most cases, a higher chance that the application is working correctly, but also that it's updated frequently. If you search for "Blue light filter" or similar in the Google Play store, there should be a couple of applications to choose from. Let us know if you find an application that you really like!
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