The tone of human skin can vary, Von Luschan's chromatic scale is often used to classify skin color for the purpose of assessing sun tanning risk.  6 skin types are distingguished as follows:

    Type I: von Luschan 1-5 (very light).
    Type II: von Luschan 6-10 (light).
    Type III: von Luschan 11-15 (intermediate).
    Type IV: von Luschan 16-20 ("Mediterranean").
    Type V: von Luschan 21-28 (dark or "brown").
    Type VI: von Luschan 29-36 (very dark or "black").