Idiom: You look like you have just seen a ghost!
Example:
Joe: Jane! Are you all right? You look like you have just seen a ghost!
Jane: I just got really shocking news from my doctor. We are having triplets.
Joe: 3 babies?!
Jane: Now YOU look like you have just seen a ghost!
Meaning: You look like you have just seen a ghost is an expression used when someone has a shocked or scared look on their face.