Brave the Elements

• WWizards of the Coast2009-10-01
  Official Ruling
  Only white creatures you control at the time Brave the Elements resolves gain the protection ability. Creatures that come under your control later in the turn, or that turn white later in the turn, won’t have it.
• WWizards of the Coast2009-10-01
  Official Ruling
  You choose a color as Brave the Elements resolves. Once the color is chosen, it’s too late for players to respond.

Rulings via Scryfall