Using Supernatural Stamina on a Zombie Creature with Diregraf Colossus on the board
Supernatural Stamina adds a Triggered Ability to the (in this case) mummy that has an Effect of returning the mummy to the battlefield when it dies. This is not the same as casting a spell so it does not Trigger the Ability of the Diregraf Colossus.


  601.2. To cast a spell is to take it from where it is (usually the hand), put it on the stack, and pay its costs, so that it will
  eventually resolve and have its effect. ...