I've seen shadows like that many times. Blackish but with blue grains. As others have said, the film was underexposed. If you're scanning, you can fix this with curve-adjustments and noise-reduction in software, but that's a hassle. I prefer to rate Fuji 800 at EI 400 whenever possible. With a 50mm f/2 lens wide open shooting at 1/30 or 1/15, EI 400 should handle about everything indoors.