https://www.yahoo.com/creators/lifestyle/story/barbara-eden-on-i-dream-of-jeannie-why-it-started-in-black-and-white-and-5-other-surprising-facts-035508670.html

Barbara Eden is joining fans in celebrating the 60th anniversary of "I Dream of Jeannie". The 94-year-old star has revealed secrets and stories from the set, and some may surprise fans.

The article is saying the first color episode aired on 12/18/1965 (episode 14 of the first season). All references I've seen say the entire first season was filmed in black and white.

It's plausible that episode was filmed and broadcast in color on NBC, since they had done that with other shows in the past. Even though the first season animated opening was shown in black and white, it was probably produced in color.

I don't know about that Yahoo article.

The story that I'm familiar with is: Sidney Sheldon wanted the series to be in color from the beginning, 1965-66 season, but those in charge at NBC weren't all that confident that the show would succeed, so black and white episodes were ordered for the 1st season to save on production costs. When the series proved to be more popular than anticipated and renewed for a 2nd season, color episodes then went into production, which was mandatory anyway as all prime time shows for 1966-67 had to be in color. 1965-66 was the last season prime time shows could be in black and white. In 66-67 everything went to color.

With regards to Barbara Eden's pregnancy in the 1st season, again, the story that I'm familiar with is that to go along with her basic harem outfit, she was given additional items to wear to cover her midsection so her belly wouldn't show.