I am a LEO and I will tell you what the state law says and then tell you my personal experience and belief.
C.R.S. 18-18-101 discusses specific types of knives with blade lengths OVER 3.5 inches, but does not include hunting or fishing knives. They are inlcuded in an affirmative defense that can be brought up in a prosecution. Butterfly knives fall into the gravity knife definition.
Switchblade knives are discussed in CRS 18-12-101 and are illegal for possession. An affirmative defense can be raised by law enforcement members, members of the Armed Forces and National Guard on official duties or has a valid permit or licenser for possession of such a knife. I've never heard of a permit or license for a switchblade knife.
For the most part, Colorado law does not regulate or control any knives with a blade less than 3.5 inches.
As a LEO, I've never given anyone a hard time for having a knife on them unless the knife was used in a crime. I've never pulled out the ruler and measured, although the general rule of thumb is to use the width of your palm. I can't remember any officer I've worked with giving anyone a hard time about knives, again, as long as the knife wasn't used in a crime of some sort.
It is my unofficial belief that most law enforcement are not concerned with knives as long as they remain clipped or sheathed on a person that the officer does not deem a threat.
I know. It doesn't clear the air on the matter. Just my $.02.