Funny. I started a separate thread on this.
When I lived in Italy, I learned that the deeper green an Olive oil the better. Of course, if they're adding soy oil and nut oils, why wouldn't they add a coloring agent as well? Most of these companies have an 800 number you can call. I would call and ask them about tests they have done
to guarantee their oil is pure. I know that that is like asking the Big Bad Wolf what he did with Grandmother, but I think they'll get nervous and start telling the truth if enough people start cracking on them. Otherwise they could be liable for a class action suit. (I hate frivolous law suits, but this is one of those times I am glad we have this weapon).
One American distributor that I think we can trust is Bragg's. They make only a few products (Olive oil, Amino acid blend (a bit like soy sauce) and Apple Cider Vinegar). They're health nuts, and I would tend to think their products are what they say they are.