I wondered how I would do it, but I soon came up with a "good" idea one night when I was at home. I use an air popper when I eat popcorn so I used that. I sprayed it as usual with an olive oil spray; however, I colored the olive oil with a couple drops of red food coloring first. It worked like a charm! It looked really cute in the blue cups of "Princess Popcorn," but I don't think I'll be trying this again for good reason. My hands were stained an odd red color for about a week and I always had that "greasy hand" feeling.
So, you have been warned. There are ways to color popcorn the color you want, but try to find another way besides coloring olive oil spray; otherwise, you will have very bright and very soft hands from both the coloring and the spray. You have been warned!
*EBL