The Colorado constitution was amended in 1910 to add the initiative process, which lets citizens sponsor proposed new state laws or proposed amendments to the state constitution, and submit them to a vote of the public.

As of 1995, initiatives have been limited to single subjects. See Article V, section 1(5.5). The Title Board is charged with making the initial determination that an initiative concerns a single subject and, if it does, setting a ballot title that is fair and not misleading. The decision of the Title Board can be appealed to the Colorado Supreme Court. Sometimes the proponents appeal, but more often an objector appeals. You can view initiatives that have been challenged in the Colorado Supreme Court since 2006 with the links on the left-hand side of this page.

Historic initiative issues in Colorado have included:

• Prohibition. In the very first election in which initiatives were allowed, in November 1912, voters were asked to enact statewide a prohibition on the manufacture and sale of alcoholic beverages. They refused, 60 percent to 40 percent.
• Prohibition went into effect in Colorado in 1916, however, and in 1918 the state’s voters closed certain loopholes in the liquor ban by adopting “bone dry” prohibition, 64 percent to 36 percent. But they repealed Prohibition in 1932, a few months before the federal government did.
• Women’s Rights. In 1914, Colorado voters were asked to let women serve on juries if they were willing. The voters – including women, who had been voting in Colorado since 1893 -- said no.
• Annexation. In 1974, Colorado voters enacted the Poundstone Amendment, which prohibited governments from annexing territory without the consent of the voters in the affected area. The measure was aimed particularly at stopping Denver, where public school students were being bused for racial integration purposes, from annexing areas from surrounding counties.
• Official English. In 1988, Colorado voters amended their state constitution to make English the state’s official language.
• State Revenue and Spending. In 1992, Colorado voters limited state government spending each year based on inflation and population change, requiring refunds of revenues in excess of the cap to be refunded to taxpayers. The voters amended the measure in 2004 to relieve state budget woes.
• Amendment 2. Passed in 1992, the nationally controversial measure prohibited cities from outlawing discrimination against homosexuals. The U.S. Supreme Court later ruled it unconstitutional.

Ballot title appeal briefing schedule for 2025
Petition filed on or before March 21, 2025: 20 days simultaneous opening briefs/20 days simultaneous answer briefs
Petition filed on or before April 11, 2025: 14 days simultaneous opening briefs/14 days simultaneous answer briefs
Petition filed April 12, 2025 or later (November ballot): 7 days simultaneous opening briefs/7 days simultaneous answer briefs

Chronological listing of Colorado initiatives and referenda, 1912 - Present, Colorado Legislative Council: http://www.leg.state.co.us/lcs/ballothistory.nsf/