There's no specific law against balisongs or butterfly knives in the CO Revised Statutes, but prosecutors can claim that they're gravity knives, which would make them illegal weapons (in the same category as switchblades). Possession of an illegal weapon would be a class 1 misdemeanor.
You might try talking to your local District Attorney and see what they have to say about the issue. I wrote to the Denver D.A.'s office several years ago and they said that they do consider balisongs to be gravity knives. (See
here.)
It's something that you can argue in court (and you might be successful if you have a good lawyer), but you'd have to consider if it's worth it .