All of the following are color units of measurement EXCEPT?

The term "dominant" is not recognized as a standard color unit of measurement in the context of color theory or cosmetology. In color discussions, the other terms—volume, hue, and shade—are commonly used to describe specific aspects of color.

Volume refers to the measurement of how much developer or peroxide is mixed with color, which plays a significant role in the overall effect of the hair color. Hue denotes the actual color or pigment itself, such as red, blue, or yellow. Shade is the variation of a color that includes black or gray (to make it darker) or the intensity of lightness and darkness without introducing new hues. These definitions illustrate why option "A. Dominant" stands out as not fitting into the category of established color measurements.