This is my newest modern build as of 5/7/2016, took me about two months to trade and buy all the cards needed for this deck, which has huge potential for turn 4 wins.
Prismatic Omen allows one to set up a lethal Scapeshift on turn-four, proactively defend against Blood Moon, and handily win by dealing incremental damage even without resolving a copy of Scapeshift.
Consider a sequence as follows:
Turn one: Land; Serum Visions (optional)
Turn two: Second land; Farseek, Explore, or Sakura-Tribe Elder
Turn three: Repeat of turn two; Prismatic Omen
Turn Four: Sixth land; Scapeshift for all four copies of Valakut, the Molten Pinnacle plus any two additional lands.
With exactly six lands in play (four of which are copies of Valakut) one can deal as much as 72 damage, SAVAGE! Of course, this kind of sequence cannot be expected to happen regularly nor without any interaction from the opponent. Prismatic Omen helps to incrementally kill the opponent off of successive Valakut triggers in the event that Scapeshift is not successfully cast. This provides a reliable alternate route to victory that proactively contributes to the normal game plan. Lightning Bolt is another card that is somewhat contentious an inclusion in Scapeshift decks. Although Lightning Bolt is excellent against aggressive strategies such as Affinity,Infect, and Nacatl Burn, it is a weak card against control decks and other combo decks because it does so little in the way of advancing the game. The fact that Prismatic Omen turns every land drop into an individual Valakut trigger means that winning via incremental damage becomes a viable backup strategy to the Scapeshift plan. This makes Lightning Bolt a convenient inclusion, as it can be turned to the face when no creature-targets exist, and in so doing contribute to this backup plan.
