Zoe, remember that a lot of cotton hakama dyed with indigo blue dye will color transfer to your dogi and any other surface for a while. You will need to "set" the color most likely. I'm sure someone here can tell you how. As I recall, it has to do with soaking the garment in vinegar or something like that.
Common myths, time to bust them again...
1. Vinegar does not "set" dye. It simply can't and doesn't.
2. The dye doesn't get "set" by anything you can possibly do to the garment. The garments have been overdyed; ie, more dye is sitting on them than their fibers could have possibly absorbed. Because, guess what? It looks and feels better to sell that way.
Your job is not to glue the dye to the outside of the garment; it's to get rid of it by repeated rinsing. Vinegar won't do anything but make it smell like you want to eat salad. Just keep washing in mild soapy water and rinsing over and over until the excess dye floats away.