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To get your white rubber soles white again, try using white-wall cleaner (designed for tires). Follow the package directions for cleaning tires. You could also try ice skate cleaner that you can purchase from a sporting goods shop.
I haven't tried this yet, but it sounds harsh.
I LOVE the Majic Erasers which also work great to clean crock style shoes.
Mr. Clean magic eraser works very nicely on rubber shoe soles; especially on white.
this stuff just might work