From the video description:

The Manila folder is a staple of the office environment, but it's also a titan of media - it appears in detective thrillers, crime dramas, spy comedies and mundane slice of life office sitcoms. But why? How did it become so prominent? Well it all starts in the Philippines.

While file folders, as well as file envelopes, are no longer solely made from abaca fibers (aka Manila hemp), the color it lent to its products still is used as a default in file folders.