I've got a couple more for you.
"The Mel Torme Show" on CBS, aired its first episodes in September and October of 1951 in color, and then switched over to B&W in November. Same for the "Mike and Buff" show, which was a live talk show produced in NY featuring Mike Wallace and Buff Cobb.
The "Ford Theater" series was also broadcast in color on NBC from 1954 to 1956. Broadcasts reverted back to B&W though for its final season on CBS between 1956 to 1957. This was the first series regularly shot on color film, according to Wikipedia.
"The Lucy Show" was filmed in color beginning in 1963, but broadcast in B&W through the 1964-65 season. Also, the pilot for "Voyage to the Bottom of the Sea" was filmed in color, but aired in B&W. The show then switched over to color in its 2nd season, in 1965.
A salient passage from a Wikipedia article on color TV re some other possible candidates...
Several syndicated shows had episodes filmed in color during the 1950s, including The Cisco Kid
, The Lone Ranger
, My Friend Flicka
, and Adventures of Superman
. The first two were carried by some stations equipped for color telecasts well before NBC began its regular weekly color dramas in 1959, beginning with the Western series Bonanza
NBC was at the forefront of color programming because its parent company RCA manufactured the most successful line of color sets in the 1950s, and by 1959 RCA was the only remaining major manufacturer of color sets.
CBS and ABC
, which were not affiliated with set manufacturers and were not eager to promote their competitor's product, dragged their feet into color.
CBS broadcast color specials and sometimes aired its big weekly variety shows in color, but it offered no regularly scheduled color programming until the fall of 1965.
The first color TVs didn't actually go on sale to US consumers until 1954, so not many people saw those early 1951 CBS colorcasts. The National Production Authority banned the manufacture and sale of color TV receivers to consumers from late 1951 to early 1953 ostensibly because of the Korean conflict. So that's undoubtedly the main reason why color production and broadcasts effectively ceased during that period. Also, the initial NTSC standard for color broadcasts wasn't approved until December of 1953.
There are undoubtedly a number of other series in the 1950's, and possibly the early 1960's which had pilots or early episodes filmed in color, which then went back to B&W due to lower production costs, changes in network affiliations, or the slow rate of color TV adoption. I couldn't tell you which ones, off the top of my head. But I'd concentrate my searches on early color shows on NBC and CBS during the 1950's and early 60's. Most primetime programming was in color by the year 1966.