Enchantment, UUUU (4) Whenever an opponent plays a nonartifact creature spell that doesn't share a color with a creature you control, counter that spell unless its controller pays {X}, where X is its converted mana cost.1
Illus. Harold McNeill
If you have no creatures in play then by definition your opponent's summon spell cannot be of the same color as a creature you have in play. In this case they will always have to pay the extra mana. [bethmo 1994/06/29]
It affects Creature spells, but not Artifact Creature spells. [D'Angelo 2000/03/03]
In a multi-player game, it affects all opposing players. [D'Angelo 2000/03/03]
This ability triggers when the spell is announced. [D'Angelo 2000/03/03]
Only checks the colors of your creatures at announcement (read the word "plays" as "announces"). If your creatures change after that (even as an interrupt), it will not cause this ability to trigger. [D'Angelo 1995/10/06]
Extended tournaments (see Rule 803) have always banned this card.
Legends
(Rare)