Why is my phone screen bright white and negative display?

[AC Question]

I just got my phone on Sunday (2/17/16) and just today (2/29/16) my screen went very bright and negative at the same time. I haven't been messing with any settings, dropped it, spilled liquid on it, or done anything that could damage it somehow. The type of phone is a Samsung grand prime.

 

[belodion]

Try Settings, Accessibility, Invert Screen Colours, which may somehow or other have got switched on.