Darigaaz, the Igniter

Legendary Creature - Dragon 6/6, 3BRG (6)
Flying

Whenever Darigaaz, the Igniter deals combat damage to a player, you may pay {2}{R}. If you do, choose a color, then that player reveals his or her hand and Darigaaz deals damage to the player equal to the number of cards of that color revealed this way.¹
Illus. Mark Zug

Gatherer Card Rulings [Nov 2009]

• 10/4/2004: You choose the color during resolution. This means your opponent does not get to react after knowing the color you chose.

Format Legality	Legal in Vintage, Legacy, MTGO Classic Banned in Extended, Standard
Printings (1/6)	Invasion (Rare)