blue screen

Thanks. That looks like a display problem to me. If you do a screen shot by pressing "command+shift+3" and you don't see the blue portion then it would seem it's a display issue rather than a GPU issue.

It's something that would have to be looked at. If your Mac is old enough you may not be able to take it to an Apple Store for repair. I would contact Apple Support and ask.

Official Apple Support

Posting a screen shot would be helpful. When you reply insert the screen shot using the Image insertion icon at the bottom of the reply window.