'Course, not only was that a 3rd party disc (tho chances are the one-color issue affects the Nintendo titles too), who's to say they might not transition to full color labels later? It is cheaper to just do it in blue, and they've got to get as many copies out as possible for launch, so maybe the extra expense wasn't worth it.
Anyway, If I hear about one person in the entire country who either doesn't get a Wii or returns their game because the label on the disc isn't in multiple colors, I will turn in my Know-It-All badge.