So I was standing outside, waiting for the train. I was tired so I closed my eyes for a while. Then when I opened them, the world was a lot more blue than it normally is - why is this? I tried it a couple more times to be sure that it wasn't just a mistake, which confirmed it, as the world kept being blue (of course, not permanent, it slowly gets back to the "normal" colors).
I'd appreciate a simple explanation, as I'm not a biology or physics student. I only have a very basic understanding of both subjects. Thanks in advance!