Go all the way through your Colorado return, past the Income section, past the Credits section, and continue until you see a screen with the title, Qualifying for the Colorado Sales Tax Refund. Answer the next two questions and the amount will be included on your return.
TABOR stands for Taxpayer Bill of Rights and it says that when Colorado has a surplus in revenue, it is refunded to taxpayers in various ways. One way is through the state tax return. See more information here.