Final answer:
Density is the only option not related to color units of measurement; it pertains to mass per unit volume in physical substances. When a color is fully saturated, it is at its brightest and most vibrant state.
Step-by-step explanation:
Among the options provided, all are color units of measurements except density. In the context of color theory, saturation refers to the intensity or purity of a color — when a color is fully saturated, it is at its brightest and most vibrant state. Concentration, although often associated with solutions in chemistry, can relate to the density of a color within a mixture. Finally, 'dominant' can be tied to the dominant hue in color theory, although it is not a color unit of measurement.