The Blonde, Brunette, Redhead trope as used in popular culture. The hair equivalent to vanilla, chocolate and strawberry (dessert flavors) or Yellow, Blue, .
The sheer number of different shades and tones of hair color account for the unusual color names to be found. This melanin comes in two forms: eumelanin, which is responsible for creating black and brown shades in the hair, and pheomelanin, which is responsible for red and yellow.
Although there is some debate over this, the Oxford Dictionary definition of brunette is: noun: a woman or girl with dark brown hair. This source.