Indigo Dying by Susan Wittig Albert (2004, Paperback, Reprint)

Everything in the very small town of Indigo is going well until Casey Ford, the town bully and owner, announces his decision to sell the mining rights to the town. This spells the end of Indigo, population 37. While after strip mining the place everything will be "put back into place" by the miners, the area would never be the same ecologically. When Casey walks into one of his own booby traps (or does he?) a chain of events occur leaving China Bayles as blue as indigo dye. As usual a lot of information on herbs is given, this time on herbal dying.