I don't think you "get it."
White balance is selected with film camera's by using specific film.
White balance with digital is done by selecting the corresponding setting.
What is White?
Under different lights, white varies. You don't NEED a filter or a gel - you have to set the white balance properly so that the camera KNOWS what white is.
If you shoot RAW, you can do this later in the computer, if you don't shoot RAW, then set the white balance in the camera. Once the camera "knows" what "white" is, it will compensate for the type of lighting.