Legal without Permit requirements except in the City and County of Denver. Also there are places that are marked off limits to open carry. Carrying a gun in a private vehicle is legal. This does not extent to public transportation. No permit is required. The minimum age for open carry is 18.
What is Open Carry?
Open carry is the ability to carry a gun in plain view. Some states require a permit to open carry, and some do not, but most have restrictions on where it is legal to open carry.