yesterday after waking my Macbook Air (Early 2015) with macOS Sierra from sleep I was greeted with gray login screen. Now I have gray every time I wake up my Mac.
First time I had the same color as background on dock for some reason but that went away after I disabled "Reduce transparency" in Accessibility settings.
I did some googling and found that this may be related to FileVault (since everything is encrypted OS presents gray background) however I had FileVault turned on since I got my Macbook and never encountered this gray thing.
What is the cause? My main worry is that it might indicate some problems with my computer. Thanks.