July 25, 1967: During its broadcast of the TV series Combat!, ABC aired a commercial for a soft-drink called Squirt. The commercial appeared in color. What made this unusual is that it appeared in color even on black-and-white TV sets.
The commercial used a technology developed by the Color-Tel Corp., and patented by James Butterfield, that used pulses of light to trick the brain into thinking that it was seeing color. Butterfield described this as “subjective color”.
The company had informed the media before the broadcast, but most people didn’t know it was going to happen, and so they thought they were going nuts when they suddenly saw flashes of color on their black-and-white sets.
The technology had some limitations. It could only be used for still images. Also, the colors were muted and flickered a lot. But the really big problem was that the technology emerged just as color TVs were becoming popular. So it was a clever gimmick that no longer had much practical purpose.
More info: Chronicles from the Analog Age Blog
Also worth noting: the idea of being able to see color images on a black-and-white set was the premise of a famous April Fool’s Day hoax that occurred in 1962 in Sweden.