Page 12 of Colorado Big Game Brochure from Colorado Parks and Wildlife states that there can be a total of 6 rounds in the chamber and mag combined. I would venture that since if you get caught breaking laws while hunting you can lose your hunting license for life (same for if you get caught poaching). Therefore I would say even if the law doesn't specifically state it, just block off a mag with a temporary block. Or buy a 5 round mag. I just don't think it's worth the risk of losing the ability to hunt. I have heard that these limits don't apply to varmint such as coyotes.
http://wildlife.state.co.us/SiteColl...me/biggame.pdf