We already reported about the dark theme which was spotted in the leaked Windows 10 Build 10056. Apart from the Notification Tray and Start Menu, a new registry hack allows users to enjoy dark theme throughout the OS. When you have this registry enables, several apps like Settings, Alarm, Calculator and others change to dark theme.
DWORD value: 0
Windows Phone OS already allows users to choose between dark and light themes, Microsoft is now bringing it to the PCs with Windows 10.