You can get to Device Manager by right-clicking on the Windows icon on your Start Bar. The Device Manager will populate, click on Display Adapters- a twistie will open - Double click on Intel HD Graphics 520 - The Properties will open - click on Driver (second tab) - Select Rollback Driver. It will ask why you are rolling back your driver, I selected that my computer wasn't working as before.
I too got the crazy grey screen on my Aspire R14. I seriously thought something more was wrong with my computer, I thought the worst. Simple fix and I am glad I don't have to take it in for repairs!
Hope this works for you! -Alexandra