I would assume ebony would either be clearcoated , black stained wood, or maybe more of an ultradark grey.....But I have no Idea how they really look next to each other.
Try to find a guitar shop that has both, and put them next to each other.....
I wouldn´t recommen buying a guitar by looks anyhow
According to dictionary.com, one definition of ebony is "Black in color."
I bet that manufacturers use "ebony" rather than "black" because "black" is not an exotic, expensive wood, and doesn't sound as fancy.