Oh, good. I was looking and looking for that and missed it. I thought I remembered him saying something to that effect. So, sure, the hall is clean-ish.
I figured with a hole in the brain pan it was leaking enough odd color blood to give another explanation for what they were seeing, even if Esmerelda's blood was in the mix. Sadly, I was remembering a reference to the creature's blue viscera, which isn't the same thing. Oh well...