How long do I have to file a lien in the state of Colorado?

I am a general contractor who has a signed contract with the home owner. They have paid a deposit, but owe the balance on the job. The job is complete to contract specifics "and then some". It is a small single family condo. The work was being performed while the house was under contract to be sold, the contract fell through and now the owner is liable for payment. do I only have 2 months to file a lien or 4 months. The letter of intent was sent out 2 weeks ago.