The use of black and white or color in old movies was largely driven by the evolution of film technology over time. In the early days of cinema, most movies were shot in black and white because the technology for capturing and reproducing color was still quite limited and expensive. As the technology improved in the 1930s and 1940s, color films became more common, but many filmmakers continued to use black and white for artistic or stylistic reasons.
The iconic film The Wizard of Oz from 1939 is a prime example of how filmmakers used the contrast between black and white and color to enhance the storytelling. The opening scenes in Kansas were shot in black and white, creating a dull and dreary world. When Dorothy enters the magical land of Oz, the film dramatically shifts to vibrant Technicolor, reflecting the newfound wonder and adventure. This creative use of color was a powerful tool for filmmakers to capture the audience's imagination and transport them to different worlds within the same movie.