Real or Fake License Plates?

I wonder if those 666 license plates (Colorado green and white ones) or the ones that have KKK on them (again, Colorado green and white ones) on the highways are real or fake? I've seen at least a dozen of those on I-25 near Thornton, Colorado now, combined (both types of plates). They're usually on white, maroon, or dark blue pick-up trucks, or sedans, American brands, not new looking, but ten years old looking. They aren't commercial plates. Red, white and blue are the only other things (vehicle colors) that I've noticed, beyond the plates. They seem illegal, and I think they must be making these license plates somewhere.