Weird picture display on Macbook Pro, what would cause this?

So just before I opened up my Macbook Pro (2016 13-inch running Sierra 10.12) and my desktop as well as all the pictures on it had all the colours distorted like someone had turned up the contrast really high or something. I restarted and the issue is resolved, but my question is really just what could have caused something like that to occur? Would it be because I shut the lid earlier without putting it into sleep (which I have done before, and probably shouldn't) or something else? It doesn't mean my Mac has a bug or has been hacked or something while I've been off it does it?