The reason we shouldn't update on the "room color" evidence has nothing to do with the fact that it constitutes anthropic evidence. The reason we shouldn't update is that we're told, albeit indirectly, that we shouldn't update (because if we do then some of our copies will update differently and we will be penalized for our disagreement).

In the real world, there is no incentive for all the copies of ourselves in all universes to agree, so it's all right to update on anthropic evidence.