F25 Recommendations for henna for highlights /tints on dark hair

I have dark brown - black hair and am looking to use henna to add some natural highlights. Which is the best brand that doesn't have any chemicals added available in India? On the henna sub they say adding things like aloe/indigo can change results - please share if you've tried to do something similar and your method. When I've tried previously I had very subtle tibts that only showed in the sun