Mistaken use of Control-Y (CTRL-Y) to Redo

CTRL+Y is Proof Colors, very top of the View menu.

View > Proof Colors

Thank you so much. It worked 

OMG I HAVE THE SAME ISSUE, how can these guys have such a horrific UX? ctrl + y is used pretty much everywere as an undo control but here, itjust messes everything up and does something that no one knows nor wants. Really these guys i feel like i wnt to ill people right now. and don't offer a way to fix it? wtf just happend to my design

ctrl y is answer of ctrl y ( outline)

FIXED: VIEW - PROOF SETUP - INTERNET STANDART RGB (sRGB)

Oh Jesus..it happened to me for the third time when I accidentally changed the keyboard settings while working..thanks for the post! I could manage to get back everything as it was before. 

It sounds like you do hours of work on a single layer, the one you were able to copy and paste to another document, instead of preserving most of what you do by using multiple layers, smart objects, adjustment layers, paths, et cetera.

Or at least you did way back when you wrote that.

Since this came up in search results, I'm going to write a suggestion for anyone reading it: 

Constantly editing a single layer and counting on Undo for any revisions is generally a mistake, for multiple reasons:

Editing like that is called a Destructive Workflow

• By using it you are forced to give up all subsequent edits when you undo.
• You also lose your undo chain when you save and close the file.
• Oh, and if you ever learn Illustrator, its design team are blindered about undo, and won't even let you see your edit history like in Photoshop, so you have to undo blind. 

Instead, use a Non-Destructive Workflow:

• As a simple starting point, any time you're going to make some radical change, you can simply hit control-J to make an extra copy of the layer before it's altered. You can end up with a small stack of layers that show major steps in the process of creating the finished product. But you can gradually move on to steps that give you a lot more power to control previous changes you made to the image, as follows...
• If you keep each new paste or image on its own layer, you then can revise each of those layers separately, preserving most of what you'd done since, and can "undo" after reopening the file.
• And layers can usually be turned into "smart objects", which then secretly keep an original version of that layer, with all of the changes you make to it preserved separately, so you can turn off a change or even adjust it later.
• You can't erase bits of a Smart Layer normally, but you can create a Layer Mask that lets you conceal parts of the layer EXACTLY as if you were erasing them. You "paint black" on the mask and where you paint becomes invisible, and you can then unerase parts by painting white over the black.
• You can also change all of the visible layers at once non-destructively, with "adjustment layers" that alter what every layer under them looks like. 

what is the answer exactlz _ i canät seem to find it , iäm having the same problem 

In Photoshop 2018 this toggles the Proof Colors option. To untoggle the options, go to the View Menu in the top toolbar and click Proof Colors to uncheck it if it's already checked.

hold control and press the eye on each layer and everything will show again