Resolved Windows windows color change

I don't know how but I suddenly got all my windows changed to have a light blue color instead of white as I was working. I have looked at Settings but cannot see how to fix this? This is very irritating as I also just had to have Windows reloaded as some Windows files had been corrupted! Now I have lost all my outlook personal folders including all my contacts plus my programs (e.g Google etc) during this process.

Help?

 

Fixed - PC to Screen adapter was loose on the monitor!

 

I like blue. My desktop

 

Thanks for coming back and posting your solution.