says... Accepted answer #1
Technically the mana symbol is in the reminder text and not technically part of the cards color identity, so yes, it is perfectly legal. :) I use it in mine and I love it. Along with Nirkana Revenant of course.
November 28, 2014 12:18 a.m.
To expand a bit:
Color identity takes into account the mana symbols in a card's mana cost and text box except for mana symbols in reminder text (text in parentheses). Additionally, it takes into account any color indicators (the colored dots in typelines, such as on Garruk, the Veil-Cursed Flip or Pact of Negation from MMA) and any characteristic-defining abilities.