They were originally in color. Also, they weren’t released for TV initially. These shorts were released in theaters, similar to how the trailers in modern screenings are released today. It was only in the '50s when these shorts were broadcast on TV.
Over half or slightly more were in black-and-white at the time, that didn’t mean that color films didn’t exist. Even ignoring Technicolor, there were color film experiments and even some feature films. Some films were even only partially in color (Rio Rita '29 is a good example).
At this point in 1942, Technicolor was important enough for filmgoers to not see color films as constituting a very tiny minority of films released.
And yes, these shorts were shown together with black-and-white films as well.