Help friends htc one s screen is turning purple...anyone know whats up?

[TheLoganmills]

My friends htc one s just started getting a purple-ish tinge to it and I just assumed it had something to do with cold weather, but now its spread across the whole screen and he can't even read text anymore. Looked online but couldnt find any other cases of it? Has anyone had this problem?

 

[nickarli]

Do they have the app 'JuiceDefender'?
If so, is 'Night Tint' enabled?