Text (4th+errata): Target spell or permanent becomes red. (Its mana symbols remain unchanged.) [Oracle 2001/08/24]
If played on a spell being cast, it changes the color of the spell. If the spell becomes a permanent, the permanent enters play with an effect on it that changes its color. [WotC Rules Team 1998/05/01]
Extended tournaments (see Rule 913) have banned this card since 1999/10/01.
Note - This card was of type Interrupt and is now of type Instant. [Oracle 1999/09/03]