The team also re-signed defensive end Ebenezer Ekuban, who missed all of last season after rupturing his right Achilles' tendon in a preseason game against Dallas.
Denver severed ties with both Walker and Gold late last week. The Broncos tried to trade Walker, but couldn't find any takers and released him to avoid having to pay him a $5.4 million option bonus on Tuesday.
Gold, who spent seven seasons in Denver sandwiched around a season in Tampa Bay in 2004, was released after his performance tailed off last season.
Colbert, 25, played four seasons with the Carolina Panthers and had 109 catches for 1,424 yards and seven touchdowns. He was a second-round pick out of USC in 2004.
Koutouvides, 26, has been with Seattle the last four seasons, and is a standout on special teams. Last season, Koutouvides finished fourth in the NFL with a career-high 20 tackles on special teams. The former Purdue player was selected by the Seahawks in the fourth round in 2004.
Copyright 2008 by The Associated Press