Yes, you read that correctly. All the nonartifact creatures on the battlefield have to be the same colour in order to get the bonus. Not just all your creatures or all an opponent's creatures or even all creatures you don't control; it has to be all or nothing. Flavour-wise, that just doesn't make any sense really. Why would your opponents' creatures be supportive of your cause when your cause is to kill them? Why can your creatures have a Concerted Effort or Mobilize on their own, but they have to be the same colour as everyone else to shard a common cause?
Okay, enough ranting on the fact that this doesn't make sense of a flavour level. If I had the money, I'd run Jihad if I wanted an effect like this. It's not so much that every nonartifact that makes this card bad. It's the fact that it gives all nonartifact creatures the bonus, including your opponents'. Outside of Slivers, giving your opponents' creatures positive effects/abilities usually never works out in your favour.
Pros: Good sized buff
Cons: Universal buff, hard-to-meet condition