Hairprint did NOT work at all. Not a single grey hair was affected. I followed the instructions precisely and for nearly 2 weeks before application, I performed all the precautions and preparations ie. no hair products, use chelating shampoo etc.
The biggest disappointment is that Hairprint does not stand behind their product ie. they will not refund if their product does not work. Here's an excerpt directly from their customer service:
"We do not guarantee the Hairprint True Color Restorer outcome nor do we offer refunds on used products."