Yes, if contracted for in the loan docs and properly disclosed, when the payment is more than 10 days late you can charge a late fee up to 5% of the unpaid portion of the payment for consumer credit transactions loans secured by real estate. For more particulars check this section of the UCCC out.
Source: Colorado Statutes : TITLE 5 CONSUMER CREDIT CODE : CONSUMER CREDIT CODE : ARTICLE 2 FINANCE CHARGES AND RELATED PROVISIONS : PART 2 MAXIMUM FINANCE CHARGES AND OTHER FEES AND CHARGES : 5-2-203. Delinquency charges.
http://198.187.128.12/colorado/lpext.dll?f=templates&fn=fs-main.htm&2.0