Shades are independent colors. Even if they don't have a name. The entire concept of color is a human conceptual one not one that exists in physics. When you get right down to it there are no natural colors that are actually one color. Even the best single wavelength emitters output in a range around an average wavelength not one color.

A typical human can only see about a million colors we can't differentiate finer than that.

People trained with color reference swaths can do better