If they're looking to save on fuel costs by using diesel, this is the wrong country to do it in. The price difference between gasoline and diesel is higher than the gain in fuel economy. You'd be losing money running diesel. That being said, the 3.0L diesel will be showing up in the colorado sooner rather than later.The engineers are probably driving it to save on fuel costs, and there are "currently no plans to bring a small diesel engine for trucks to the U.S. market", I'd expect Bob Lutz or Wagoner to say. "Please take a look at one of the V8 Silverados piled up on our dealer lots."
Which would be ridiculously ironic. Because "Americans don't want small trucks or small diesels" (just GM engineers when they are transporting stuff, and trying to get a job done).