The only restriction to firearms in vehicles is that long guns / shotguns and muzzle loaders must be 'unloaded', and you must not be a prohibited person.
LOOK I followed rule 5!! hehe
Tell that person to read THIS 'law'.. it's the real one..
"It is unlawful for any person, except a person authorized by law or by order of the division, to possess or have under his control any firearm, OTHER THAN A PISTOL OR REVOLVER, in or on a motor vehicle unless the chamber of the firearm is unloaded."
This goes on and states an officer can inspect the chamber of a shotgun or rifle in a motor vehicle..
Others CRS citations:
CRS 18-12-105 (states you can conceal in car / home without permit)
CRS 18-12-105.6 (limitation of local ordinances preventing carry in car)