18th Century Colour Wheel
Found a bit more: “In the late 18th century, Moses Harris elaborated on the Newtonian color wheel by charting not only pure colors, but the various shades of those colors as well. If we consider the Newtonian wheel to be a one-dimensional representation of color, then Harris’s wheel introduces a second dimension.”
I have no idea who wrote that since I copied it straight from a forum board. Apologies!