Robert Sarnoff, 78, who helped usher in the era of color television and who aired the first televised presidential debate while heading NBC, died of cancer here Feb. 22.

Mr. Sarnoff dedicated the first all-color television station, the NBC-owned Chicago station, in 1956, four months after he became NBC's president. He stepped down as president in 1965.

"We are committed to color and intend to make the transition as fast as possible," Mr. Sarnoff said soon after taking the network's helm.

He also was credited with inviting Vice President Richard M. Nixon (R) and Sen. John F. Kennedy (D-Mass.) to the first televised debate of presidential candidates, in 1960. Three years later, "The Huntley-Brinkley Report," the network's nightly news program, was extended from 15 to 30 minutes.

During Mr. Sarnoff's years as network chief, NBC launched its weekend news program "Monitor," which aired features, interviews and entertainment. The popular TV program "Bonanza," a one-hour western saga of the Cartwright family, began running in 1959 and ran through 1973.

In 1962, the network gave birth to the first 90-minute-episode series, "The Virginian."

Under Mr. Sarnoff, NBC was a pioneer in integrating television. It was the first network to have a program hosted by a black singer, Nat King Cole. In 1965, Bill Cosby became the first black actor with a leading role in an hour-long prime-time series, "I Spy."

Mr. Sarnoff was born in 1918, a scion of one of broadcasting's first families. His father, radio pioneer David Sarnoff, built Radio Corporation of America into one of the country's great corporate monoliths. After working as RCA's president and chief executive, Robert Sarnoff was chairman of the board from 1970 to 1975. RCA has since been purchased by General Electric.

Mr. Sarnoff graduated from Harvard University in 1939. As a Navy communications officer during World War II, he supervised the installation of radio links to islands in the Pacific.

After the war, he worked briefly in newspapers and magazines before joining NBC in 1948. Five years later, he became the first president of the Radio and Television Executive Society and one of its governors. He also served as chairman of the New York Stock Exchange.

Survivors include his wife, Anna Moffo, an opera singer; three daughters; and two brothers.