Hello,
Thank you for reporting this crash, although Answerhub is for issues related to Unreal Engine 4 in particular. For support with Fortnite and for reporting these crashes, please go to http://fortnitehelp.epicgames.com/
It will crash and the screen will go one full color kinda random sometimes greenigh sometimes orangish or brown. The only way to stop it is to turn off the comp via shutdown not even restart is a sure fix.