My 'Primary Colors for Kids' app is nearing completion as well, and I should be able to get it in store next month. The app is aimed at 18mo-2 yr olds who are just learning the concept of colors. For many kids this is challenging since often the things they come across have more than one color and more than one characteristic - a kid focuses on its shape, name, texture, size, and color and sometimes is hard for a kid to acknowledge the color as some special feature of a picture or a thing.
My app tries to offer several pictures, of course, with names of color and offering an idea of the color as a special characteristic of the picture.
I'm adding a little puzzle in as well. We'll see how it goes.