Photoshop CS2 - This one was more just experimentation with color. I went way overboard with the saturation though, as whenever I look at it, I slightly squint and ask myself "what's the point in that?".
In any case, it pretty much was just a case of laying down different strokes, then having a hint of dark to represent the grooves. Finally on top of that, just the same layer duplicated three times, each with a lighter, darker, and mid-tone gave the appearance of a dent. These were set to multiply by the way.
