iphone 5 fade to purple

When the brightness is up higher than the lowest it can be my phone screen fades out to purple and the touch screen becomes unresponsive. My friend (didn't know that this was happening) turned my brightness up to 100% and now the screen fades out instantly. I cannot unlock my phone to turn the brightness down, as I can't 'swipe up' to do so.

Someone please help! What is happening?

I have an iPhone 5, on the latest ios.