How do you make green, purple and brown

Anyone here taking music appreciation at connections academy?

Silverpoint is a. a technique using the blackish residue of impure carbon obtained by removing water from animal and vegetation substances. b. a technique involving the use of a metal point, and a thin silver wire, popular in the 14th and 15th centuries. c. a printmaking technique born from crayon manner that imitates the appearance of chalk lines. d. a technique used since the 16th century involving a stick filled with either colored or black graphite, a heated mixture of carbon and clay

What argument does the author make in this excerpt from cannibals all! or, slaves without masters, written by george fitzhugh in 1857?