I put this together a while ago but it is an easy cheap and cool mod. You can use clear paint, plastic, paper, what ever you can find that will allow the apple to still glow. and it doesn't have to be perfect because the apple is on the inside of the case. I recommend stained glass spray paint. This will not loose adherence and will still peel of if you want to remove it. Here is the link to my little blog.
http://modapple.blogspot.com/