I was initally thinking it was red as it was like a fireblast. As you said, dump some guys, do some damage, and then sew the game up. However, you are locking the game up in an indirect, and less guaranteed manner. However, I don't know where this fits exactly in the color pie. (Though i will confess it works great with Cursed Scroll).
I just want to make sure that we don't pigeonhole this as discard, as it is much more conditional (no effect on graveyard, is not always advantageous to use, effects both players).
Artifact: I don't think this fits artifact theme, unless it was progressive (each player discards a card until they have none, etc)
Red: might fit tempo, flavor, and style, though possibly too powerful at 3CC.
White: definitely fits theme of global effects, gives white discard, use the counter version? Sharahazzad precendent

Blue: The anti-draw card card. Is this card anti-blue?
Black: fits discard theme, fits personal riskiness theme (it could hurt you too), though does not have cards go to graveyard
Green: I don't see it fitting here
Any other thoughts. I'm more interested if this card has a niche or use......