But be warned, once you start down the path of understanding color perception and vision you will find that it goes on and on and on. And then on and on. Its not simple.
Many optical illusions are essentially bugs in the perception system, that is, the image is causing the perception circuitry to see something that isn't actually there (e.g. motion when there is no motion, colors, when there are no colors, etc).
I spent a day trying to recreate the illusion with other images, and I think I know what is going on that causes the illusion for me. But I have not yet found anyone else that the illusion works on. One thing I find interesting is that, for me, this is a robust illusion. I see it every time I look at the picture.