Corporal Colby was a member of Company D, 1st Battalion, 32nd Infantry Regiment, 7th Infantry Division. He was listed as Missing in Action while fighting the enemy in North Korea on December 2, 1950. He was presumed dead on December 31, 1953. 

Through the work of the Defense POW/MIA Accounting Agency, the remains of Corporal William Colby were accounted for in 2024. His name is permanently inscribed on the “Courts of the Missing” at the Honolulu Memorial.