Anti juice.

Just in case anyone's wondering, Granny (mum) used to use sard wonder soap on the washing.  She would get really mad at us for blow-darting mulberries around - not because of the stains, but because of the wastage.  She was happy to let the birds eat all the berries off the top half of the tree, but would not to let us deliberately throw good fruit about.
For cleaning our skin we were taught to take a green mulberry and crush it in our hands, rubbing the squished moist pulp into the purple juice stains, and then wash with regular soap.  It worked!