Colo. Rev. Stat. § 38-26-103
Every laborer, mechanic, ranchman, farmer, merchant, or other person performing any work or labor or furnishing any laborers, materials, ranch or farm products, provisions, goods, or supplies to any contractor or subcontractor in the construction of any railroad, reservoir, or irrigation canal, or any part thereof, used by such contractor or subcontractor in carrying on said work of construction whose demand for work, labor, laborers, material, ranch or farm products, provisions, goods, or supplies so furnished has not been paid may deliver to the company owning such railroad, reservoir, or irrigation canal, or to its agent, a verified account of the amount and value of the work and labor so performed or the laborers, material, ranch or farm products, provisions, goods, or supplies so furnished. Thereupon such company, or its agent, shall retain out of the subsequent payments to the contractor the amount of such unpaid account for the benefit of the person to whom the same is due.
C.R.S. § 38-26-103