Conley died Sunday of stomach cancer at her Los Angeles home surrounded by family and friends, Eva Demirjian, a publicist for the CBS serial drama, said Monday.
She was diagnosed with cancer about three months ago, and the show's producers were deciding how to portray the fate of her character, Demirjian said.
"She constantly entertained us with every move, every breath, every inflection of her voice. Whether she was the villain, the damsel, the sexpot or the comedienne, Darlene was brilliant," said Bradley P. Bell, the show's executive producer.
She started on the long-running soap in December 1988, playing the flamboyant, red-haired chief of Spectra Creations and rival to Forrester Fashions. Her portrayal of Spectra earned her two Daytime Emmy nominations for best supporting actress and six Soap Opera Digest awards.
Daytime television "is really the best medium today for women of a certain age to do something really flashy; it's where what we do well as actresses matters," Conley once said.
The Chicago native began her acting career at 15 when she was cast in the touring production of the Broadway hit "The Heiress."
After graduating from high school, she appeared in several stage productions, including "Cyrano de Bergerac," "The Baker's Wife" and "Night of the Iguana."
She later found work in front of the camera, making small appearances in the movies "The Birds" and "Valley of the Dolls" and such television shows as "Murder, She Wrote," "Cagney & Lacey" and "The Mary Tyler Moore Show."
She landed meatier roles, however, on daytime television in the late 1970s, playing a range of characters on "Days of Our Lives," "General Hospital" and "The Young and Restless."
Conley, who was divorced twice, is survived by her son, Raymond Woodson, and sisters Carol Fontana and Sharon Mylan.
Funeral arrangements were pending.