CF.lumen is one app I cannot live without, it filters the bluelight on the display of Android phones, even those which aren’t rooted.
But, rooted devices have an exclusive driver, which significantly improves the filtering, instead of placing a red overlay on the screen.
The bad news is that CF.lumen has dropped support for Android 4.4 KitKat, from version 3.60 of the app and newer, and is now only available for devices which have Android 5.0 Lollipop+ from the Play Store.
CF.lumen version v3.60 brings a new non-root overlay driver for Android 6.0 Marshmallow, which will automatically disable itself, when you have a security prompt for granting permissions. The root driver is also new. for a full change log refer the Google+ post from Chainfire.
Download CF.lumen for free from the Google Play Store:
[appbox googleplay eu.chainfire.lumen]
You can still download older versions of CF.lumen for Android 4.4 KitKat from the official XDA thread, which has v3.00 and v3.16 APKs available.