I have a macbook pro 15" 2016. I plugged in my external 27" 1440p gaming monitor and was messing around with the refresh rates in my display settings. I changed it to 144hz from 60hz and now all I see is a white screen. I was unable to revert it back to 60hz. So every time I plug in my external monitor my screens (macbook and display) goes white. I can't see what I'm clicking so I can't change it back. Any suggestions on how I can fix this?