Why the red?

This is kind of a cross-post from Kwaidan (1964). I noticed that at least a couple of K. Kurosawa movies have ghosts in red. I noticed that the color red was used prominently in all of Kwaidan's stories. Is there some sort of symbolism in Japan with red that I'm unaware of? Or maybe Kurosawa's just referring back to that film? Help me out here!