If you control no Homunculi when the second ability resolves, nothing happens. There’s no penalty for failing to sacrifice a Homunculus.

The Homunculus you sacrifice due to the second ability isn’t limited to being a Homunculus token put onto the battlefield by Puppet Conjurer.

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.