Red creatures you control get +1/+0.

White creatures you control get +0/+1.

{R} {W} , Exile this enchantment: Exile all creatures you control. At the beginning of the next combat, return those cards to the battlefield under their owner's control and those creatures gain haste until end of turn.

Rulings

The beginning of the next combat will happen even if the player whose turn it is doesn't intend to attack with any creatures.2013-04-15
A creature that's both red and white will get +1/+1 from Legion's Initiative.2013-04-15