reflection 5

I just got back from benaroya hall. I noticed that at the beginning of the show there was a projection of snowflakes on the walls. When the symphony started to play the projection was turned off and it changed to pinkish colored lights. I began to wonder how this happens. There had to be projectors on the wall somewhere, but I could not see them. I am curious how they do this. I would love to look in to this more.