"The show has chosen not to renew her contract," says the rep.
"Although I regret not being able to continue exploring Colleen, I have to be very grateful to the folks at Y&R for giving me my first job," Fonseca said in a statement.
Fonseca joined The Young and the Restless in 2001 in what was originally slated to be a short-term role. The actress, however, impressed show execs and the role was expanded. Fans, too, also enjoyed the actress' work. In 2002, Fonseca was nominated for Outstanding Newcomer in Soap Central's Dankies Awards.
Fonseca will continue filming scenes for The Young and the Restless through mid-April. Her final airdate -- which has not yet been announced -- will be seen in May. The role of Colleen will not be recast.