Yes, this in-shower hair-lightening treatment is safe to use on natural/virgin hair. You will see the most lightening with natural/virgin hair. Dark roots have not been chemically processed like the lengths of the hair. The darker roots will experience more noticeable lightening than the lengths because there is more melanin in the hair and it has not been chemically processed.
This in-shower hair-lightening treatment is also safe to use on colour-treated and highlighted hair. However, if your hair is intensively bleached or damaged, this product should not be used.