Icon with no transparent pixels gets funny tint in Mac's Finder

Question

Is there any special requirement for icons used by Mac applications that such icons should have transparent pixels in the top-left corner or some other place?

I'm currently trying to prepare a Mac build of a Unity3D-based game and noticed that if the icon of the game is a full-bleed square with NO transparent pixels, it gets some funny green-red-yellow tint when shown in Finder in small size (when viewed in List, Columns or Cover Flow). The icon is displayed fine on Desktop or if the folder is viewed in "as Icons" mode.

If the icon has a transparent frame, no such problem happens. I don't know anything about Mac development and neither googling or searching here brought up anything helpful, but sorry if this is really a basic question. Is it maybe a bug of Finder on Mac? I have 10.7.5 and Mid-2012 13' MacBook Pro.

The issue happens with this icon:

But doesn't happen with this icon:

Answer 1

Make sure the texture you're using as the icon in Unity is set to "Automatic Truecolor." You could be getting artifacts from whatever texture compression you're using on the texture.