If you include daytime TV, NBC didn't technically become "The Full Color Network" until November 1966, when "Concentration" began airing in color. It was the last of the holdouts, mainly because Norm Blumenthal, the producer, didn't want to show color puzzles fearing that people would guess them too quickly. He finally relented, allowing pink drawings on a maroon background instead of the old light gray-dark gray from the monochrome days.
Norm, BTW, is active on the Game Show Forums as well. Can't imagine how old he must be right now as he was probably in his late '30s/early '40s when "Concentration" was cancelled in 1973.