Lemon Juice should do the trick.
It's the citrus acid in it that removes the stains.
I used to work with a lot of mahogany that turned my hands purple.
It works for me,
Jerry

"Clemens" > wrote in message
...
>I was picking and halving walnuts, and my hands got dark brown from
> tannin in walnut's shell.
>
> Please, is there any effective agent to remove dark stains off the
> hands ?
>
> I tried with acetone, alcohol, lighter fuel, paint thiner, windex,
> washing soap, laundry detergent, but it didn't help.
>
> Thank you.