If you have armor on when you are under lava and you go to the armor screen, the gui has a wierd glitch where the screen turns a dark blood red.
steps: 1.have a full set of armor or less.
2. find some lava
3.euip the armor ( you dont have to if you dont want to )
4.jump into the lava
5.go to armor screen
6.watch the screen turn blood red
It happens too if you receive damage form hostile mobs and falls