2008-10-01 : The only difference between a colored artifact and a colorless artifact is, obviously, its color. Unlike most artifacts, a colored artifact requires colored mana to cast. Also unlike most artifacts, a colored artifact has a color in all zones. It will interact with cards that care about color. Other than that, a colored artifact behaves just like any other artifact. It will interact as normal with any card that cares about artifacts, such as Shatter or Arcbound Ravager.

2008-10-01 : You can’t sacrifice Protomatter Powder to return itself to the battlefield. First you choose the target (at which time it’s still on the battlefield), then you pay the costs (at which time you sacrifice it).