I tried this last night and it had quite a few different results, the red parts i put in changed to a pinky/orange colour, and the dust black barrel i put in changed to bronze.
However when i put parts from my mini in(all black) the barrel came out an almost gold colour, detents a bronze colour, back cap platinum colour, eye board plate a platinum to gold sort of colour. The foregrip never really changed much, there is a slight difference though. I am quite impressed with how it looks though
Dont know if anyone has tried this yet though, once you clean it with alcohol etc, if you use a felt pen you can draw on you own logos etc and have your own custom anno in the original colour.