Colomby was born in Brooklyn, New York on September 19, 1952. His father, Harry, is a jazz agent, manager, and school teacher; and his mother, Lee, is a stage Actress. While in grade school, his family moved from Brooklyn to Los Angeles. Colomby attended Beverly Hills High School and graduated in 1970. He attended classes for theatre arts at the Immaculate Heart school, where he enjoyed classic readings and decided to make acting his career.