Why called blue flim?

There are multiple theories about why adult films came to be known as "blue films." One explanation centers around the early days of cinema when films were shot silent and then hand-tinted. In the 1910s and 1920s, some erotic movies were created, and in an attempt to censors from shutting them down, producers would sometimes tint these movies blue. The theory is that this tinting process resulted in the name "blue films."