Ever since I upgraded my mid-2014 15" rMBP to Sierra, I've noticed that when loading websites in Safari, a patch of black will sometimes appear where another color is supposed to be. Example: https://puu.sh/rgvfo/53dd7fa8c6.png I cannot recall if this has happened in other programs, I want to say it may has happened once or twice. In the case referenced above, simply refreshing the page returns everything to normal. Has anyone else experienced this? Is this a sign of an underlying hardware issue? Hoping not but I have the time to go to the Apple Store this week if need be.