I've seen blue grey material on top of mine too, but it came from the yeast cake in the bottom of my primary. When i looked at the bottom of my primary before the yeast cake had diffrent layers of color : biege , grey,blue all muted though. If it is fuzzy like bread mold then it is the wrong type of fungus and possibly bad. See if you can gently and cleanly remove it w/ yor siphon or something. Or just leave it.