I am using illustrator for the first time. I have designed a logo but I think i used a short cut due to which the colors of the logo are hidden, But the colors are visible on the layers. I have checked the colors are not even gray scale. I don't know what to do now, How i Can Bring the colors back.
I think you are in Outline mode, change it back by using CTRL+Y or CMD+Y.
Outline mode is particularly handy when you've 'lost' an object behind another one. But it's quite strange to a lot of novice users.
The command CTRL+Y is Redo in most Windows programs. Redo in AI is CTRL+SHIFT+Z.