2005 prius

i think it depends on whether denver was a carb state when it was registered in 04/05. hopefully someone has more specific answer for you.

 

"Due to its preexisting standards and particularly severe motor vehicle air pollution problems in the Los Angeles metropolitan area, the U.S. state of California has special dispensation from the federal government to promulgate its own automobile emissions standards. Other states may choose to follow either the national standard or the stricter California standards. States adopting the California standards include Arizona (2012 model year),[1] Connecticut, Maine, Maryland, Massachusetts, New Jersey, New Mexico (2011 model year), New York, Oregon, Pennsylvania, Rhode Island, Vermont, and Washington, as well as the District of Columbia.[2][3] Such states are frequently referred to as "CARB states" in automotive discussions because the regulations are defined by the California Air Resources Board.
The EPA has adopted the California emissions standards as a national standard by the 2016 model year[4] and is collaborating with California regulators on stricter national emissions standards for model years 2017–2025.[5]"

United States emission standards - Wikipedia, the free encyclopedia

Colorado is not listed as a CARB state. Therefore, the Prius traction battery warranty for a vehicle originally sold there would be 8 years/100K miles.

 

are you buying it from a dealer or private, either way it could be problematic.