Commissioned in 1954 after training as an NROTC midshipman at the University of South Carolina and Penn State University, Colbus initially served in the destroyer escort USS Albert T. Harris (DE-447) and on the staff of Commander Escort Squadron 12. He had temporary duty in late 1958 on the staff of Commander Task Force 88 for nuclear weapons testing, and then was flag secretary, 1958-60, to Rear Admiral Edward C. Stephan, Commander South Atlantic Force. After he took the general line course at the Naval Postgraduate School, Colbus was executive officer of the destroyer escort USS John R. Perry (DE-1034). He had shore tours in the mid-1960s in the Bureau of Naval Personnel and as a student at the Naval War College. Back at sea, he was executive officer of the destroyer USS Basilone (DD-824) during her first Vietnam deployment, then commanded the ocean escort USS McCloy (DE-1038) in NATO ops. He was part of the program staff that developed the Spruance-class destroyers. In the early 1970s he commanded the destroyer USS Jonas Ingram (DD-938), then served on the staff of Commander Carrier Division Six. After duty in the Operational Test and Evaluation Force, Colbus was one of the initial students in the Senior Officer Ship Material Readiness Course in Idaho and later commanded Destroyer Squadron Two from 1976 to 1979. His final tour of duty prior to retirement in 1982 was as chief of staff to Commander Carrier Group Eight. The three rear admiral aviators he served were Bob Dunn, Jim Service, and Jerry Tuttle.