Chicho Ibañez Serrador wanted to shoot this series in color using film, but TVE forced him to shoot it in black & white, since Spanish TV at that time could only be broadcast in that format The color PAL system arrived Spain two years later in 1969, and it wasn't used regularly until 1973, and there was no budget to shoot it in color anyway.
Augusto Algueró didn't send the musical score in time to film the musical numbers, so they had to be filmed without music and add it in post-production.