What are some alternatives?
When comparing RedshiftGUI and SunsetScreen, you can also consider the following products
LightBulb - Background application that adjusts screen gamma, making the colors appear warmer at night...
f.lux - f. lux is a piece of software for Windows, Mac, Linux, iOS, and Android that provides a blue light filter over your screen. Research suggests limiting our exposure to blue light in the hours before bedtime can help us fall asleep faster.
Redshift Color Temperature Adjuster - Redshift adjusts the color temperature according to the position of the sun.
Desktop Dimmer - Enable darker-than-dark dimming for internal and external screens.
PangoBright - Screen dimming software that allows you to control the brightness of your laptop screens as well as external monitors.
Dimmer - A very small and free utility for Windows to reduce brightness on LCD/TFT screens.