Quintessential is described as a "dirty olive [with a Frost finish]." It's a golden brown with subtle, warm, olive undertones and a frosted sheen. It had good color payoff that went on smoothly. It was also buildable to a slightly richer, more intense color. It was very blendable. See swatches of all dupes / view dupes side-by-side.
FURTHER READING: Formula Overview, which is a detailed review of the range as a whole.