Q. Can I Open Carry in Colorado?
YES. But this is not a simple yes; unfortunately, it is quite complicated.
What exactly is Open Carry? There is no statutory definition of open carry. But put simply, it is the carrying of a firearm that is not concealed. Colorado law is silent on open carry. As it is not prohibited, it is legal. Denver has a municipal ordinance that prohibits open carry. The Denver ordinance, together with a prohibition on issuing concealed carry permits to non-Colorado residents, was upheld as not violating the 2nd amendment in Peterson v. Martinez, 707 F.3d 1197 (10th Cir 2013). http://www.ca10.uscourts.gov/opinions/11/11-1149.pdf This decision seems to conflict with decisions in other circuits, however the U.S. Supreme Court has thus far not reviewed the issue.
Does it matter if it is loaded or not? SOMETIMES.
In general, it does not change things legally if it is loaded or not. For example, in your car, the law does prohibit long guns with a round chambered, but not handguns. These are based on hunting laws. But the law concerning weapons “in facilities of public transportation” does specify “any loaded firearm.” Technically, an unloaded firearm would be legal, but a violation of this law is a felony, so arguing loaded v. unloaded is some very thin ice to skate on.
CRS section 33-6-125. Possession of a loaded firearm in a motor vehicle
It is unlawful for any person, except a person authorized by law or by the division, to possess or have under his control any firearm, other than a pistol or revolver, in or on any motor vehicle unless the chamber of such firearm is unloaded. Any person in possession or in control of a rifle or shotgun in a motor vehicle shall allow any peace officer, as defined in section 33-1-102 (32), who is empowered and acting under the authority granted in section 33-6-101 to enforce articles 1 to 6 of this title to inspect the chamber of any rifle or shotgun in the motor vehicle. For the purposes of this section, a "muzzle-loader" shall be considered unloaded if it is not primed, and, for such purpose, "primed" means having a percussion cap on the nipple or flint in the striker and powder in the flash pan. Any person who violates this section is guilty of a misdemeanor and, upon conviction thereof, shall be punished by a fine of fifty dollars and an assessment of fifteen license suspension points.