I have never come across the image file for it, always figured it was laid out in the code. I don't know much about the workings of xml and all that, but I know on a web page you can lay out a background with a hex code and always assumed that's what they did with this.
I have already used it. I have noticed that It had been needed code for display over the phone. It had quite accepted by the people and also me. I had felt many issue like I have not seen the Icons very well and also not controlled over contrast.