This new version of f.lux has a grayscale mode and new key to turn it on: Windows + End.
The big surprise is how distracting the icons on the top and bottom of your screen are. These icon colors are the kind of thing you see in candy stores and on fire alarms, but we have to ignore them just to get work done. Without those colors, your computer looks more like a magazine that can help you focus on reading or thinking—it feels different, like a sheet of paper.
Source: What’s new with f.lux