On October 28, 1960, Colbert was cast as Army Corporal Howie Burch in the episode "Two Trails to Santa Fe" of the ABC/WB western series Cheyenne, with Clint Walker in the titular role. In the story line, Burch tries to steal gold from miners working a claim near the fort where he is stationed. He is also trying to win back the affection of his former wife (Randy Stuart), whose unsuspecting husband (Richard Webb) is one of the miners. Then the Army decides to abandon the fort. Cheyenne Bodie, meanwhile, comes to the defense of an Apache woman, Aleeah (Sonya Wilde), left for dead after the masaacre of her white husband.

Colbert was married to dancer/songwriter Dotty Harmony in 1961 for 15 years. Harmony wrote for Metric Music with Sharon Sheeley and had songs recorded by Rick Nelson. They have two children, Cami and Clay. Cami is married to filmmaker Jon Freeman (Flesh Wound Films), who produces the highly successful "Crusty Demon" series of DVDs.

In 1962, Colbert played Lonzo Green in the episode "Footlights" of the ABC/WB crime drama, The Roaring 20s. Moreover, he guest starred on most of the ABC/WB series, including 77 Sunset Strip and Hawaiian Eye (seven times each), Bronco (six times), Bourbon Street Beat (three times), Sugarfoot, The Alaskans, and Surfside 6 (twice each), and Cheyenne and Lawman, once each.

In 1965 Colbert made two guest appearances on Perry Mason as Deputy District Attorney Snell; first in "The Case of the Grinning Gorilla," then in "The Case of the Hasty Honeymooner." Raymond Burr appeared as the oft-filmed attorney in this television series based on Erle Stanley Gardner's novels.

In 1966-1967, Colbert played the part of Doug Phillips in thirty episodes of the Irwin Allen science fiction ABC series, The Time Tunnel, the second lead in a show about two time travelers. James Darren and Lee Meriweather starred with Colbert. Historical events like the Alamo, the Titanic, Krakatoa, and Custer's last stand were fictionalized. In 1968, Colbert appeared in the final episode of the first season of Hawaii Five-O.

Colbert also appeared as the character Stuart Brooks on the television soap opera, The Young and the Restless, from March 1973 to March 1983, being honored at the show's tenth anniversary.

In 1981, Colbert and Robert Culp were suggested by CBS as possible replacements for Larry Hagman on Dallas after Hagman decided to hold out for more money; however, Hagman returned to the series.