Yeah, definitely do not use anything blonde. Yellow + purple = a gross mess of a color that can maybe be described as brown. I would say start with a Jeannie in dark purple.
If you're going for the same volume as the image, you'll need either extra clips to harvest wefts from, or a second long wig in the same color. Stub the built-in ponytail and use the fibers from the clip-ons/extra wig to build the ponytails around a base, almost like a giant odango. There was a really good tutorial somewhere on this site about making giant ponytails like that, I'll see if I can find it if no one else links to it. Basically, if you want it to look like hers, it's going to get costly and be a LOT of work.
If you aren't as concerned about accuracy, you can make a smaller ponytail that has some of the poof, but not as drastic. Depends on how you want to interpret it.