Your friends are probably charged with this offense:
Quote Quoting Colorado Revised Statutes 42-4-1413
Eluding or attempting to elude a police officer.

Any operator of a motor vehicle who the officer has reasonable grounds to believe has violated a state law or municipal ordinance, who has received a visual or audible signal such as a red light or a siren from a police officer driving a marked vehicle showing the same to be an official police, sheriff, or Colorado state patrol car directing the operator to bring the operator's vehicle to a stop, and who willfully increases his or her speed or extinguishes his or her lights in an attempt to elude such police officer, or willfully attempts in any other manner to elude the police officer, or does elude such police officer commits a class 2 misdemeanor traffic offense.
If your friends did in fact flee from the police, and fail to respond to attempts to pull them over, then the driver is likely to have some difficulty defeating this charge. The passengers may be able to claim that they were stuck in the car, unless they have already made statements to the police implicating themselves in the driver's decision to flee.