These are all chemical cones, not real henna.
Henna is mixed from the plant lawsonia inermis, you're right about that though all those cones contain harsh chemicals that can damage the skin and organs and even cause cancer. Black henna, henna with PPD (PARAFENILENDIAMINE) and chemically coloured "henna: are really bad and can damage you and your clients ( the fumes are too toxic too)

I wish ou could mix yuour own henna paste from henna powder and use safe, natural, long lasting oragnic henna.
Cheers.