Earlier on, we said that the Smurf cereal wasn't blue because kids would never eat a blue cereal. We now have to apologize to the Smurfs. It turns out kids will eat a blue cereal after all, but only if it has the marketing machine of Disney behind it.
It was actually just the milk that turned blue when you poured Mickey's cereal into your bowl, and that apparently constituted a magic trick. We suppose the real magic was persuading us to eat it.