The Sturm College of Law at the University of Denver maintains an online database of Colorado Legislative Council Publications dating back to 1954.  These publications include progress reports and final reports from interim committees (special legislative committees that meet when the legislature is not in session to study specific topics), and ballot information booklets, also known as “blue books”.  You can search for publications by publication number, year of publication, subject, and keywords.  All ballot information booklets can be found by searching under the subject “Elections.”