Urza's Filter + Hybrid Cards

[Hellsing293]

CC=
Artifact Rare
Multicolored spells cost up to  less to play.
It's a tool for aiding my other tools," explained Urza. "Now they'll work in harmony.

A hybrid Blue/Black creature would count as both blue and black making it multicolored, no?  Even if you can spend only 1 type of mana, the card itself still counts as multiple colors.  So, shouldn't this work?  Or is there an errata stating it only works on Gold cards?

[Apollyon]

Gold isn't a color. Hybrid spells count as multicolored (usually), so they cost 2 less with Urza's Filter in play.

[Hellsing293]

Oh, Ok.  I was wondering if Urza's Filter could somehow be used to make a combo with a hybrid card.  Didn't want to go brainstorming ideas until I knew for sure.  Thank you very much