Commanders identity

[An Angry Fatman]

if someone has an all white commander like {elesh morn, grand cenobite} can a card like {blind obedience} be in the deck because of the extort's color cost?

[Remillo]

Short answer: They can run the card.

Longer Answer: The black/white hybrid symbol used for Extort is in the reminder text, which doesn't factor in to color identity.

[An Angry Fatman]

That means that anything with an activated ability of a different color cannot be used. Ex. {lingering souls}

[Remillo]

That means that anything with an activated ability of a different color cannot be used. Ex. {lingering souls}

Anything in the text box that isn't reminder text is counted.  This includes alternate/additional costs, activation costs, and mana produced by mana abilities.  Lingering Souls has a color identity of BW, since it has B in it's Flashback cost.