My samsung 6 just completly stopped and wont work.

[AC Question]

Cant talk on phone. Front screen all black, when tried to get to work a quick flash of purple at top of phone came across screen.
What can be the problem

 

[B. Diddy]

Welcome to Android Central! First, press and hold Power and Vol Down for about 10-15 seconds to force a shutdown, in case the phone is actually frozen on a blank screen. Then try powering on again by pressing and holding Power for 10-15 seconds. If nothing happens, try charging it on a wall outlet, undisturbed, for at least 6 hours. If it still doesn't power on, then the battery or the motherboard might have failed, and you'd have to bring it to a repair shop.