Mindsparker and Multicolor

[CbStrad]

Say you have a {Mindsparker} on the board. Your opponent throws an {Azorius Charm}. Would he take 2 or 4 points since it's both of Sparker's target colors?

[Giggle the Draco Genius]

As an additional note it would have done 4 ONLY if it was written as

If an opponent casts a blue spell do 2 damage
If an opponent casts a white spell do 2 damage

It would have to be 2 separate abilities