https://leg.colorado.gov/sites/defau...219_signed.pdf

IT IS UNLAWFUL FOR ANY PERSON WHO SELLS A FIREARM, INCLUDING A LICENSED GUN DEALER AS DEFINED IN SECTION 18-12-506 (6), TO DELIVER THE FIREARM TO THE PURCHASER UNTIL
THE LATER IN TIME OCCURS:
(I) THREE DAYS AFTER A LICENSED GUN DEALER HAS INITIATED A BACKGROUND CHECK OF THE PURCHASER THAT IS REQUIRED PURSUANT TO STATE OR FEDERAL LAW; OR (II) THE SELLER HAS OBTAINED APPROVAL FOR THE FIREARM
TRANSFER FROM THE BUREAU AFTER IT HAS COMPLETED ANY BACKGROUND CHECK REQUIRED BY STATE OR FEDERAL LAW.

(2) THIS SECTION DOES NOT APPLY TO:
(a) THE SALE OF AN ANTIQUE FIREARM, AS DEFINED IN 18 U. S .0 . SEC. 921 (a)(16), AS AMENDED, OR A CURIO OR RELIC, AS DEFINED IN 27 CFR 478.11, AS AMENDED;