The following illustration using concentric circles will make color quantification easy to understand. Think of your skin tone as the center color, the color all the other colors closely relate to. Next comes the ring of colors that differ from the skin tone by a 5% contrast (difference) as measured by hue, value and chroma. Then we step out to the ring of colors that vary from the skin tone by a contrast level of 10%. In turn, the colors at 20%, 40%, [+60%, 2012]and 80-88% contrast levels are identified.
All colors inside the largest circle closely relate to the skin tone color, but only those colors that fall on the pink line (at exactly 5,10,20,40 [+60, 2012] and 80-88%) will be accepted into that skin tone's unique palette of colors.
This carefully measured selection gives your personal palette of 620 [380, 2012] colors true harmonic structure. Hues, values and chromas differ, but they differ with a precise purpose. Just as there are rules for creating musical harmony, there are rules for creating color harmony.
Until now, color analysis was more of an art than a science. Now, we can KNOW what colors harmonize, which leaves us free to trust our colors, and to confidently enjoy them.
The illustration on the left is a 2-dimensional demonstration of how different skin tone palettes relate, though in reality the space is 3-dimensional. As you see, the color palettes may overlap a little, depending on how close two skin tones are in color, nevertheless, each palette is cohesively harmonious, and only relates well with the other colors within that palette.