In pea plants, the colour of the flower is either violet or white, whereas human skin colour shows many gradations.Explain giving reasons how it is possible

Human skin colour is believed to be controlled by at least three separate genes, and inheritance of these genes is called quantitative inheritance.There can be total seven allelic combinations in the gametes of a person heterozygous for all the three genes, hece 64 combinations or gradations in colour are possible.
On the other hand, the colour of the flower in pea is controlled by non-allelic complementary genes, which independently show a simple effect.