Hmm not sure I would say that, and I'm Igbo(Ibo), both my parents are actually. I know stereotypically most people believe Igbo(Ibo) people have a lighter complexion, sometimes almost reddish/orangish, which is fairly common.
I've a lot of African-AMerican friends or Afro-Caribbean friends that could easily be Igbo but then again I could easily be from Detroit or Jamaica for the same reasons. Many black people are generally the same.
This is all in regards to black genealogy and slavery as the majority of the slaves came from Black West Africa. Of course you can tell if a person is from Ethiopia or Sudan just by physical characteristics, but that has to do with their proximity to the Arabian penninsula, and intermixing and all.