In mixing group E1 Brown we find four Browns, each with their own unique undertone. Toffee is also a Brown with a Yellow undertone, but it finds itself in the Yellows as it felt very important to the Yellow colors (This is explained in the Yellow Hue and Mixing Group descriptions).
Raw Cocoa(9) is the darkest of mixing group E1 and has a Blue-Black undertone.
Underground Brown(8) has a cool Violet undertone and works great as a go-to “Cool Brown”.
Downtown Brown(6) has a Red Orange undertone and reminds me of a Burnt Sienna paint color. It is the lightest and richest of the E1 family.
Coffee(7) has a Red undertone and is my all-purpose Brown, thus found on the Wynn Wheel and in the WynnnColor Ink Set.
All 5 Browns have been expertly formulated to be cleanly desaturated, while letting their personal undertone and individual Brown character shine through intensely. They can be used to deepen or desaturate any color with the same undertone, or used in artwork as an earthy, neutral, analogous color using the undertone as a guide.
Essentially think of them, and mix them, as if belonging to the Hue and Mixing Groups of their undertone. Trying to fit them into other groups didn’t quite work out and was more confusing than helpful. .