The cause was complications from epithelioid hemangio endothelioma, said his partner of 45 years, Patrick Horrigan.
Mr. Mitchell designed scenery, costumes and lighting, and consulted widely on theatre design. While an undergraduate at Yale, he studied with Donald Oenslager, and later assisted both Jo Mielziner and Boris Aronson on Broadway.
Mr. Mitchell's work spanned Broadway, Off Broadway, regional theatre, ballet, as well as concert designs for such entertainers as David Bowie and Emerson, Lake, and Palmer. On Broadway, he designed the musical Beatlemania, as well as Medea starring Irene Pappas and The Basic Training of Pavlo Hummel starring Al Pacino.
Other credits include the English-language world premiere of Jean Genet's The Screens at the Brooklyn Academy of Music, as well as production designs for Circle in the Square, The American Place Theatre, The Denver Center, and the Roundabout Theatre Company. His international credits include the ballet La Peri for the Paris Opera, as well as many production designs in England and Canada.
Mr. Mitchell long associated himself with classical theatre. When, in 1977, Melina Mercouri ended her seven years of exile from Greece, she starred in a production of Euripides' Medea on a set designed by Mr. Mitchell. In 1982, the National Theatre of Greece extended to Mr. Mitchell the honor of being the first American to design a classical play, Sophocles' Oedipus Tyrannos, in the ancient theatre of Epidaurus. This production became the official entry of the Greek nation to the 1983 Europalia Festival in Brussels and to the Los Angeles Olympic Arts Festival in the next year. Over the years, Mr. Mitchell designed for many ballet companies. Productions include The Lottery and L'Absence for The Harkness Ballet, Cantique des Cantiques for Les Grands Ballets Canadiens, and In Retrospect, Equinox, Under the Sun, American Rhapsody and The Veil for the Pennsylvania Ballet.
In later years, Mr. Mitchell lent his efforts to assisting dance companies with limited resources for scenic design. These included the National Dance Institute headed by Jacques D'Amboise, and the Sachiyo Ito Dance Company.
Having assisted Jo Mielziner on the design of the Vivian Beaumont Theatre at Lincoln Center and 17 other theaters across the United States, Mr. Mitchell went on to consult on the design of many theatres himself, including collaborating on the design of the Ford Center for the Performing Arts (now the Hilton) on Broadway.
In 1970, Mr. Mitchell was appointed Director of Design and Theatre Technology at the Annenberg Center of the University of Pennsylvania.
In addition to Mr. Horrigan, Mr. Mitchell is survived by his brother Fred of Lovell, ME, three nieces and a nephew.