When I lived with my Grandmother, I remember some magic she used to perform.
All the salads and vegetables from our own garden, and bought from Indian gardeners, were thrown into a bowl of water. Then Grandmother would fetch a tiny vial from the shelf in the pantry and, with the back of a spoon, remove some dark granules from it.
Then the magic happened. She threw these into the bowl and it turned into a wonderful purple. Threads of purple spun out from the little granules as they touched the water, and within seconds, the colour had dispersed throughout it.
The vegetables soaked in this solution – to kill any germs grandma told me.