Trejo was signed by the Dodgers to a minor league contract Tuesday and is with Triple-A Oklahoma City, Eric Stephen of SBNation.com reports.
Trejo cleared waivers Saturday and elected to become a free agent.
The Rockies designated Trejo for assignment Friday, Thomas Harding of MLB.com reports.
Trejo will start at second base and bat ninth in Sunday's game against the Dodgers.
Trejo is starting at second base and batting ninth for Monday's game against the Phillies.
The Rockies selected Trejo's contract from Triple-A Albuquerque on Thursday.
Rockies manager Bud Black announced Tuesday that Trejo made the Opening Day roster, Thomas Harding of MLB.com reports.
The Rockies sent Trejo outright to Triple-A Albuquerque on Friday.
Colorado recalled Trejo from Triple-A Albuquerque on Tuesday.
The Rockies optioned Trejo to Triple-A Albuquerque on Sunday.