Text (AP): Destroy two target nonblack creatures unless either one is a color the other isn't. They can't be regenerated.
Both of the target creatures must be exactly the same color or combination of colors. Both being colorless is also okay. If they differ in any way, you can still play the spell, but it does not do anything on resolution. [Apocalypse FAQ 2001/05/24]
Colors are checked on resolution. [D'Angelo 2001/05/24]
If one of the targets left play before resolution, use the colors it had at the time it left play for the comparison. [DeLaney 2001/05/24]
If one of the targets became an illegal target before resolution, this spell will still check the color of that target even though it will not destroy that target. [D'Angelo 2001/09/13]
