Looks like dying GPU or bad screen/screen cable. ( unfortunately dying gpu seems more probable as it does it only in some apps, when the screen is refreshing I think )
Can you use TV-out to see if the problem continues?
If not, you can take a screenshot with ctrl + maj + p and see if the problem show up in the screenshot.


Edit: The second video is now up and it's looks like related to what colors are displayed, it may finally be just the screen.