I am a guarantor on an apartment lease in CO, may I enter premises without permission of the tenatn? If yes, or no, please point to law

Your obligation as Guarantor merely creates an obligation for you to pay the landlord in the event of the Tenant's default.  This is an agreement between you and the Landlord to allow an otherwise unsuitable Tenant to gain possession of the rental property. Unless, there is some sort of contract between you and the Tenant or you are granted permission to enter on the Lease, you have no right to enter the property if the Tenant refuses you entrance.