Stupid question about recent version of PhotoShop

So I’m using Photoshop, and somehow I hit some weird key combo or something that makes it so that the work area–the gray area outside of the “canvas” and inside the window–is black instead of gray. I have no idea what I did, and I have no idea how to put it back. Anyone have a suggestion? Thanks.

You went into “full screen mode.” On my version of Photoshop (Mac), there are 3 little screen icons near the bottom of the tool pallette. You accidentally hit the 3rd one; try one of the other 2.

WTF? Now I fat fingered Alt+F somehow and the work area turned BLUE! I tried to make it happen again but it won’t. I’m working without my glasses because I had an allergic reaction to something last night and my right eye is blurry and swollen, so I’m not exactly sure how I fat fingered it, but something in the neighborhood of Alt+F seems to change the color of the work area. Can anyone help?

No, that’s not it. Not in full screen mode, in regular screen mode, only the color has changed.