I am not an expert on Colorado Real Estate law, so please do not rely on this as such!
The Common Law legal notice requirement - which would normally be applicable absent a statute on the point - is that notice must be given in advance of the next rental term. So, in the case of a month-to-month tenancy, you must give notice BEFORE the next rent installment is due that you will leave at the end of the next rental period. If rent is due on the first, then notice must be given before the end of the month prior to the one in which you intend to vacate. NOT on the first, NOT 30 days! You then would have to vacate at the end of the next month.
However, section 13-40-107 of the Colorado Revised Statutes appears to say than 10 days notice is all that is required in a month-to-month tenancy. Take a look at Colorado Termination of Lease for Periodic Tenancy Law - Lease - Landlord Tenant
Of course, you and the landlord can agree on anything you want - just make sure it is in writing and signed.