UPDATE: New information has come out. The green screen is exclusively for the Insider builds, the stable versions of Windows will keep the good old BSOD. The reason for the change is because Microsoft wanted an easy way to see the difference between a crash on an Insider build and the stable builds of Windows 10. It makes sense now.
A long time ago, enthusiasts would be greeted by the Windows Blue Screen of Death (BSOD) on a regular basis but in more recent years Windows has become so stable that total system crashes are a rare incident.
For reasons unknown, Microsoft decided to switch the color of the crash screen to green in the new Windows 10 Insider Build 14997. So don't be surprised if you start seeing Green Screens of Death in the future.