Colby was born Anita Counihan, the daughter of Margaret Anne McCarthy and the cartoonist Daniel Francis "Bud" Counihan,[2] a legendary figure among New York City artists and newsmen, in Washington, D.C.

Colby was hired by David O. Selznick in the 1940s to teach contract actresses, such as Jennifer Jones, about beauty, poise, and publicity.

Her job title at his production company, Selznick International Pictures, was "Feminine Director".

[6] She worked closely with Selznick's top actresses, such as Jennifer Jones, Ingrid Bergman, Shirley Temple, Dorothy McGuire, and Joan Fontaine.

Colby died of lung disease at her home in Oyster Bay, Long Island, on March 27, 1992, aged 77.