Chainfire's screen modifying app CF.lumen has been updated to v3.0 with a few important changes, not least of which is a mode for unrooted devices. You won't get full functionality, but it's better than nothing, right? If you want to verify that, you can also get all the pro features for free now. Seriously.
According to Chainfire, the night mode and color adjustment features from Chainfire3D and the original CF.lumen Gingerbread apps are frequently requested. So frequent, in fact, that they're back for KitKat+ devices as CF.lumen on the Play Store.
If you've ever used f.lux for your PC, you know basically what to expect here - color temperature adjustments based on the time of day, bringing tones more in line with your eyes' expectations when the sun goes down.