If you are unable to file your Colorado income tax return by April 17, 2012, you may file under extension. This means you may file your return by October 15, 2012. There is no form to submit to get approval to file the Colorado return by October 15. However, the extension of time to file DOES NOT allow you to extend your payment due date. You must pay at least 90% of your tax liability by April 17 and the remainder by October 15 to avoid delinquent payment penalties.

Pay Online through Revenue Online (https://www.colorado.gov/revenueonline/_/#1) by credit card or e-check.
 
Pay by Mail by sending in a payment with the Payment Voucher for Automatic Colorado Extension for Individuals (DR 158-I).
Mail the voucher to:
Colorado Department of Revenue
1375 Sherman St.
Denver, CO 80261-0008

Form DR 158-1 (Extension of Time for Filing a Colorado Individual Income Tax Return): http://www.colorado.gov/cms/forms/dor-tax/CY158i.pdf

Return this voucher with check or money order payable to the Colorado Department of Revenue, Denver, Colorado 80261-0008.