Dictionarium polygraphicum. To dye horns...

Dictionarium Polygraphicum:
Or, The Whole Body of Arts Regularly Digested.
Vol I.
London: Printed for C. Hitch and C. Davis in Pater-noster Row, and S. Austen in St. Paul's Church Yard. MDCCXXXV.
1735
To dye HORNs, &c. RED.
First boil the horns in alum water; then put it into tincture of Brazile in alum water for fourteen or twenty days, or into a tincture of Brazile and milk.

To dye HORN BLUE.
First boil it in alum water, then put it into a dissolution of indigo in urine.

To dye HORN of an emerald GREEN.
Put as much fileings of copper into aqua fortis as it will dissolve, then put in the horn for one night.