Excel - search for missing values and return these values based on 3 columns - MATCH/INDEX/IF combo?

This gets a bit too expert for me, hopefully one of you can help me!

See the image for what I am trying to achieve. The red text shows what I want. List3 contains all the possible values for List1. List2 displays the currently active values for List1, and I want to return the missing values based on List3.

I'm guessing I'm looking at a MATCH/INDEX/IF function but I cannot figure this one out. Anyone out there willing to give me a hand? <3 Thanks a bunch!