Most shadow people are pitch black. They're solid basically. It would be like a silhouette... Also, most people think shadow people have red eyes but they don't. Demons can take the shape and form of shadows at times and those are the ones that have the red eyes. How do I know? I'm a medium. 

Now, you may or may not want to argue the case with me, but shadow people don't have red eyes. I've always came across shadow people in my life and not one of them had red eyes. In fact, I have one shadow person as a friend, a benign fellow of course, but one thing- he doesn't have red eyes. I am a channeling medium, and I know many many things about ghosts and other worldly things due to this gift, and I'll tell you this: I have seen one shadow like thing with red eyes- but it was no shadow person. It was in fact a demon- a demon who protected me and hated my parents (which I understand why at that moment) but besides the point, that was a demon- not a shadow person.