From the FAQ page: Important information regarding Concealed Handgun Permits and Background checks.
According to the Federal Firearms Regulation Reference Guide:
Yes. At this time, Colorado Concealed Handgun permits do not meet all the criteria to qualify for an exemption to the background check. That means even if you have a Colorado Concealed Handgun permit you must have a new background check every time you purchase a firearm. Out of state Concealed Handgun permit holders also need a background check to purchase a firearm in Colorado.
Note: All InstaCheck statistics are in a PDF format. Click here for a free download of Adobe Reader.
Contact the ATF Distribution Center
P.O. Box 5950 Springfield VA, 22150-5950
(Please order 6 months worth of forms. Forms are free of charge)