Demi-permanent dye faded already?

I asked a question a little while ago, about getting my first hair dye. I got a demi-permanent, visibly darker than my real color, with some red tints. (This was on Monday) I waited until Wednesday to wash my hair, like she said, and used the proper shampoo. But now, my hair looks mostly the same as it did before, with just a bit of red around my bangs.

Could it be that I was seeing it wrong earlier? Or did it really go back to the natural color in 4 days?