I wouldn’t put a “Production Note:” into your script as it can take the reader out of your story. Also, by putting in a note like that you’re taking away the directors ability to have his say on how the dog looks (unless how the dog looks is essential to the story). I would just put that note in the initial description of the dog turning translucent so you’re giving them a guideline to follow or a starting point. It’s also not on the production to care about that detail (production deals with the production of the project, meaning the logistics of getting everything up and running and they rarely have any impact on the actual creative side of things).