Willy Wonka and the Chocolate Factory - Blueberry Tube
When Violet is chewing the gum that's a meal and she starts blowing up, look towards the bottom of her right foot and you'll see a tube coming out of her pant leg.
You can also see a blue glare on violets hair. Which suggests they shined a blue light on her to make her look bluer. Why didn't they just use more face makeup?!
They do use face make up for Violet. When the Oompa Loompas are rolling her back and forth before they take her out, you can plainly see that she is wearing face make up.
They used the light when they wanted to make violet lighter in color, then they used the makeup when they had to move her, and couldn't spotlight her. There is a distinct moment when they change.
I researched the movie and they didn't use a dummy when Violet becomes a blueberry. They had to do all these other special things and the Oompa Loompas had a terrible time rolling her out of the room, but the producers never said anything about using a dummy.