when we got our gi as kids (the yellowy ones) we used to shrink them in the bath and whiten them at the same time by soaking them in bleah in the bath.
bleach is ace it kills everything. try this? or take it to a dry cleaners, they have solvents to remove everything.
the dryer used to leave black marks on the kits, so it was drip dry from then on-which takes like for ever.