Colbert made the announcement via Twitter thanks to some nice Photoshop work.
Joe Fann of 49ers.com had also announced the news hours earlier.
Colbert appeared to become frustrated in November and throughout the season by the comparisons his former number, 38, brought to former hard-hitting 49ers safety Dashon Goldson, who spent his first six NFL seasons in San Francisco.
The 49es made Colbert a seventh-round draft pick out of Miami last year. He registered 37 combined tackles, five passes defensed, and two forced fumbles during 14 games and six starts in 2017.