It's a nice story, even if it isn't true.
When I Spy premiered, NBC officials seemed pleased that only three stations—in Savannah and Albany, Georgia, and Daytona Beach, Florida—refused to carry the show. It was seen, however, on 180 other stations covering 96 percent of the country.
...and I Spy
had a black co-star.
In 1959 or 1960, during Twilight Zone
's first season, Serling did an episode featuring an entirely black cast called "The Big Tall Wish." I'm not sure how well-received it was -- and the fact that TZ never again did an episode featuring an all-black cast suggests to me it may not have gone over well -- but I'd argue that that one episode was far more ground-breaking than was Star Trek six years later.