You can go to packing.org and they have the knife carry rules listed. Basically anywhere except Denver City you can conceal carry up to 3.5" and in Denver I believe it is 3.0". Open carry I believe is okay if it is a hunting/fishing knife is used in hunting event. I ask a Lt in the Northglenn PD and he kinda laughed and said he could care less is I had a sword in my truck. What ya going to do? Try to weild it from a truck? I had a boynet that I kept next to my seat in my truck so I could cut my seat belt if I needed to in an emergency. But now I just carry a kershaw knife which is for sure legal in Colorado. Kershaws are great, faster than a switchblade and cheaper!!
Colorado - Criminal Code Section 18-12-101. Definitions...
(e) "Gravity knife" means any knife that has a blade
released from the handle or sheath thereof by the force of
gravity or the application of centrifugal force, that when
released is locked into place by means of a button,
spring, lever, or other device... (f) "Knife" means any
dagger, dirk, knife, or stiletto with a blade over 3-1/2
inches in length, or any other dangerous instrument
capable of inflicting cutting, stabbing, or tearing
wounds, but does not include a hunting or fishing knife
carried for sports use. The issue that a knife is a
hunting or fishing knife must be raised as an affirmative
defense. (j) "Switchblade knife" means any knife, the
blade of which opens automatically by hand pressure
applied to a button, spring, or other device in its
handle... (a.3) "Ballistic knife" means any knife that has
a blade which is forcefully projected from the handle by
means of a spring-loaded device or explosive charge.