Which of these U.S. TV shows did not debut in black and white?

It says Bonaza, not Bonanza.

We just got the blu-ray set of the original series. They transferred them directly from the masters and they are glorious!

Is Bonaza wrong because they misspelled it?

Player FishRman, You are correct. Bonanza was billed as the “in color” western from its debut. It was part of NBC’s Sunday night color line up.

Lots or Gray horses in Bonanza as I recall...

I believe that the series Bonanza was started by RCA and was shown in color to sell more color television sets. So, the answer to this question has two correct answers.