[andrewljohnson]

This article pointed out that a red button amidst a green palette converted better in one instance, because the red button contrasted starkly. That's also my current theory on how to make an app icon.

For my App Store apps, I choose loud colors that contrast well with other apps in the category. I look at how the icon stands out in searches on iPhone, iPad, and iTunes. I still want a beautiful icon, but my primary concern is whether it pops.

Unfortunately, it's hard to test the theory.

[Ciotti]

That's interesting, I'm unfamiliar with what sort of data is available for App Store users, I'm assuming there's no way to really test the performance of different icons?