John DeMarco was a San Diego native. While growing up his family moved back and forth between the east and west coasts, living in different parts of the country for short periods of time.

John's interest in color theory was first developed while studying with James Clark in San Diego. Later studies were done at Chouinard Art Institute in Los Angeles.

DeMarco worked as an art director and creative director for numerous studios and agencies. He also was a counselor and art teacher in the UCSD Department of Psychiatry's Narcotic Treatment Program for Drug Abuse at Deer Park in Escondido. He painted murals in San Francisco (the Haight), Los Gatos and San Diego.

John lived and studied in Spain for three years, with solo exhibitions in Madrid, Torrelodones and El Escorial.

John DeMarco's work is collected by people throughout the United States, Spain and Italy. His work continually changed, moving from surrealism to figurative portraits (many of which are blues and jazz musicians), to humorous works that commented on various forms of social conduct.